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A. Paul www.pnas.org/cgi/doi/10.1073/pnas.1809378115 zone cloudy Einsle F. meteorite Joshua the of properties Nanomagnetic ftemtoieprn oysitral eeae magnetic generated internally presence body’s the in parent form meteorite tetrataenite of the magnet islands of permanent As poten- 4). rare-earth a carrier (3, for as potent materials well replacement a two as sustainable These zone meteorites tial T). in cloudy information 2 the paleomagnetic to make of (up to coercivity combine tetrataen- nm, magnetic properties of high 10 symmetry tetragonal generates Small than ordered ite content. less L10 Ni single-domain) the to (i.e., local while magnetized states, the nm uniformly and 500 promote rate sizes over island cooling tetrataenite from the T of on diameter at depending Islands in forms (2). vary zone decomposition can spinodal cloudy of The process 1). (Fig. (ordered zone” islands to tetrataenite Fe–Ni) of Fe (fcc intergrowth taenite of and nanometer-scale range Fe–Ni) a (bcc a kamacite Widmanst of spanning centimeter-scale intergrowth familiar features the cool- from metallurgical scales, Slow length distinctive (1). today to core rise iron liquid (∼ the its of ing by planetesimals field generated magnetic differentiated the is of like Earth gen- much cores formation, were iron their as after fields liquid such shortly magnetic the meteorites, that by in evidence erated minerals preserve Magnetic alloy, system. 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A.S.E., Z.S., analyzed J.F.E., B.H.M., research; A.S.E., research; performed J.F.E., tools; designed R.J.H. reagents/analytic R.J.H. and P.A.J.B., and R.B., P.A.M., Z.S., A.S.E., J.F.E., contributions: Author for unsuitable soft is the and that place, time retained take insufficient is to crystallo- fast, taenite ordering too the phase Fe–Ni is along the ferromagnetic rate aligning for cooling available axis the is easy If tetrataen- c-axis. magnetic of graphic the structure (5). tetragonal with are ratios, ordered them ite, equal the within nearly form in ordering Fe, to Fe–Ni and required Ni tetrataen- of of the planes degree a (002) of the Alternating at size and the cooled islands both which ite nanopaleomagnetic affects of meteorite, rate preservation Cooling the iron remanence. to sLH conducive is IAB that zone rate Tazewell cloudy the the of study in micromagnetic and tomographic of bined intensity the to zone theory field. cloudy quantitative magnetic the a parent-body of develop the to state quest magnetic the the in linking questions step these essential to an answers is Providing open. remanence secondary remain acquire postcooling, to zone the cloudy and the cooling, the of during susceptibility about acquisition questions remanence primary further of and timing the unknown, by remains recorded zone is cloudy information paleomagnetic how (8– precisely Despite approach 11), (7). “nanopaleomagnetic” new scales this submicrometer-length of successes on notable state zone magnetic cloudy the the ability quantifying of of The capable are imag- which 6). magnetic a methods, X-ray became ing high-resolution (5, preserves of recently advent polarity only zone the with information and possible cloudy paleomagnetic intensity this the extract field’s that to the proposed of been record has it field, b lcrnqedsTcnlge elIfrain IAE Campus, MINATEC l’Information, de Technologies des electronique ´ owo orsodnesol eadesd mi:[email protected] Email: addressed. be should correspondence whom To ie Saghi Zineb , piiesnhtcaaouso h luyzn o industrial for zone applications. cloudy to the pathways of potential analogues toward synthetic optimize point findings, and, our zone cloudy by the inspired into paleomag- encoded becomes which information by netic mechanism the micromagnetic discover nanometer We and simulations. of tomography resolution combination subnanometer state-of-the-art to are a archi- zone using magnetic and cloudy tecture, crystallographic, chemical, the 3D its of how to to properties linked explain alternative magnetic we sustainable remarkable Here a the magnets. potent as permanent a promise earth-based shows is rare sys- also only solar but early not the tem from It information paleomagnetic meteorites. of carrier found metal-bearing nanocomposite Fe–Ni occurring naturally in is zone cloudy The Significance ee ebgnt drs hs susb efrigacom- a performing by issues these address to begin we Here, b NSlicense.y PNAS eateto aeil cec n Metallurgy, and Science Materials of Department d enM Collins M. 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EARTH, ATMOSPHERIC, AND PLANETARY SCIENCES cloudy zone. The size of the tetrataenite islands (bright regions) decreases systematically from 150 nm adjacent to the rim to less than 10 nm at a distance of several microns away from the rim. This change from “coarse” to “fine” island sizes is caused by a decrease in the local Ni concentration with increasing distance from the rim, which in turn lowers the temperature at which spinodal decomposition initiates during cooling (thereby reduc- ing the diffusion length and time available for coarsening of the islands). The matrix phase (dark regions) appears to percolate throughout the entire cloudy zone. We reveal the true 3D struc- ture of the cloudy zone through the complementary approaches of 3D Energy Dispersive Spectroscopy (3D-EDS) and APT (see Materials and Methods). Due to the similarity in mean atomic number between the two different Fe–Ni alloy phases, conventional scanning trans- mission electron microscopy (STEM) using the high-angle annu- Fig. 1. FIB-secondary electron micrograph of the interface region between kamacite (bcc iron) and taenite (fcc Fe–Ni), which forms part of the lar dark-field (HAADF) signal does not resolve the internal Widmanstatten¨ intergrowth in the Tazewell meteorite. Kamacite (Left) is microstructure in the cloudy zone (Fig. 2A). The Fe-rich matrix followed by a rim of pure tetrataenite (Center), which then gives way to (Fig. 2B) and the Ni-rich tetrataenite islands (Fig. 2C) are clearly the cloudy zone (Right), a nanoscale intergrowth of tetrataenite islands resolved through the acquisition of an EDS chemical map at surrounded by an Fe-rich matrix. The cloudy zone transitions from coarse each angle of a tilt series. The spectral signals are denoised using tetrataenite particles (>150 nm) to fine tetrataenite particles (<50 nm) with principal component analysis (PCA), and the total intensity asso- increasing distance from the tetrataenite rim. The matrix phase (dark in the ciated with the FeKα peak (Fig. 2B) and the NiKα peaks (Fig. image) percolates throughout the entire cloudy zone. 2C) are integrated. The resulting tilt series of chemical maps are reconstructed to form a quantitative 3D volume of Fe and Ni concentrations using a compressive sensing (CS) algorithm nanopaleomagnetic analysis. The quickly cooled Bishop Canon (14, 15). ◦ IVA meteorite (∼2,500 C/My) demonstrates such soft magnetic In the coarse cloudy zone (Fig. 3A and SI Appendix, Movie behavior, characterized by the presence of large, meandering S1), we observe two large tetrataenite islands (blue). The sam- magnetic domains throughout the cloudy zone, consistent with ple volume is shown as reconstructed by STEM-EDS tilt-series the absence of tetrataenite (10). If the cooling rate is too slow tomography and visualized as surfaces of constant intensity, ◦ (<0.5 C/My), the tetrataenite islands grow to such size that termed “isosurfaces.” The intensities defining the isosurfaces they develop multiple magnetic domains. In addition, the coarse were defined by the strong contrast between the two phases in the length scale of the cloudy zone in slowly cooled meteorites Ni maps to reveal the morphology of the matrix and tetrataen- leads to the conversion of the metastable, paramagnetic, fcc ite phases. In the coarse cloudy zone (Fig. 3A), the tetrataenite matrix phase to a more stable, soft ferromagnetic, bcc martensite islands contain continuous threads of matrix phase (yellow) run- phase, which further degrades and complicates the paleomag- ning through them. The matrix threads form a mostly continuous netic properties. Both phenomena are observed in the slowly network of 10 to 30 nm-diameter structures, with occasional cooled mesosiderites (12), making them unsuitable for nanopa- small isolated patches of matrix contained within the tetrataenite leomagnetic study. A “Goldilock’s zone” for cooling rates exists, islands. whereby cooling is slow enough to enable tetrataenite formation Fig. 3B and SI Appendix, Movie S2 show a region of the yet fast enough to prevent the tetrataenite islands growing to intermediate-fine cloudy zone. With smaller island sizes, the full sizes that are beyond their single-domain threshold and to main- 3D shape of some of the tetrataenite islands in this tomographic tain the metastable, paramagnetic, fcc structure of the matrix volume are recovered. We use best-fit ellipsoids as a represen- phase. These considerations constrain usable meteorite sam- tative metric for island size within the tomographic volume (16, ples to those which have experienced parent body cooling rates 17). In the intermediate region of the cloudy zone, we find the ◦ ◦ between ∼0.5 C/My and ∼150 C/My (12). With a cooling rate major axis diameter to range from 18 nm up to 100 nm. Compar- ◦ ◦ of ∼20.8 C/My at 500 to 600 C (13), the Tazewell IAB sLH ison of the major, intermediate, and minor ellipsoid axes yields a meteorite displays a well-preserved cloudy zone that has not prolate tri-axial symmetry with the ratio of major/intermediate been affected by shock and is well within the desired cooling-rate and intermediate/minor axes ranging from ∼1 to ∼2, with an window for nanopaelomagnetic studies. We present a multiscale, average of ∼1.2 (we caution, however, that the small number of multidimensional study of the cloudy zone in the Tazewell mete- orite, yielding structural, crystallographic, and chemical informa- tion across the entire cloudy zone, in three dimensions and at nanometer to subnanometer spatial resolution. This information provides the input for micromagnetic simulations of both individ- ual tetrataenite islands and small clusters of islands, which have far-reaching implications for nanopaleomagnetic studies of plan- etesimals as well as for our understanding of the thermodynamic and structural behavior of possible replacements for rare-earth permanent magnet materials.

Results A 3D Structure of the Cloudy Zone. A 2D cross-section through the interface region of the Widmans¨atten intergrowth in the Tazewell meteorite is shown in Fig. 1. A region of kamacite Fig. 2. (A) STEM HAADF micrograph of the coarse cloudy zone. (B) Iron (far left) is followed by a ∼ 1 µm-thick rim of tetrataenite, concentration map collected with 3D-EDS. (C) Nickel concentration map which is then followed by the island/matrix nanostructure of the collected with 3D-EDS.

2 of 10 | www.pnas.org/cgi/doi/10.1073/pnas.1809378115 Einsle et al. Downloaded by guest on September 26, 2021 Downloaded by guest on September 26, 2021 Cliff–Lorimer 5B. Fig. in seen as phase, aver- each mea- an for produces APT spectrum measurements Our age with 3D-EDS uncertainties). the well greater of very significantly quantification with (see agrees examined (albeit and also surements Methods) was datasets and 3D-EDS Materials the in informa- composition contained chemical tion The statistics. counting on based 81.95 be 0.36 and to Ni, found is phase matrix isee al. et Einsle The be 5A. to Fig. in found proxigrams is the particles in tetrataenite seen that 49.61 as of gradient wide, composition compositional nm average sharp 2 a just to (Fig. is APT corresponds using matrix measured to was zone cloudy 4 the and medium, of coarse, regions in Zone. phase fine matrix Cloudy the and the islands tetrataenite of Composition Chemical to close the the aligned that observe demonstrating was to particle, needle able tetrataenite are the we in 4D, planes Fig. atomic In zone. cloudy the informa- about geometrical this tion reliable For most determined phases. the two provides robustly the 3D-EDS of reason, the fraction volume affect these absolute or not However, chemistry process. do assump- reconstruction artifacts to the reconstruction sensitive during highly is made this tions as is APT, geometry oblate by particle an that constrained noted possess poorly be here should seen It ratio. volume general, aspect In the spheroid isosurface. in the fitting measured of best extent islands the the the on of based axis nm, 4A. major 20 Fig. the at in ellipse estimate shown tip we the particles, in these in contained iden- only For fully these, are provided 32.5% of volumes needle; these of are APT of content the 8 zone within Ni islands cloudy tetrataenite a 260 the by tify defined of Isosurfaces parts Appendix). other APT (additional of needle same studies the from These collected less). or datasets nm two 30 are of diameter and long with 4 particles (tetrataenite (Fig. APT of use the through be not may values these representative). that means observed particles medium complete the (B) and coarse zone. cloudy the medium the (A) of volume the for reconstruction and (C yellow blue zones. in in depicted cloudy phase particles tetrataenite visibility matrix the the Fe-rich enhance rectan- with to A features, In removed shown. small lines. been are of has emission cut”) isosurfaces, X-ray (“corner termed K subvolume intensity, gular Ni constant characteristic of surfaces the B, using series tilt EDS 3. Fig. S5 A h Dntr fafiergo ftecod oewsexplored was zone cloudy the of region fine a of nature 3D The .Fg 4 Fig. ). and ± (A–C .6 e 50.00 Fe, 0.16% B Dvsaiain ftmgahcrcntutosfo STEM- from reconstructions tomographic of visualizations 3D ) A and ± and igepaeo otolc”fo h etro the of center the from “orthoslice” or plane single A ) .2 o h ro rsne seult SD 2 to equal is presented error The Co. 0.02% .Tetasto rmtetrataenite from transition The Appendix). SI B hwATdt rmtefiecod zone cloudy fine the from data APT show ± .6 i n 0.39 and Ni, 0.16% h100i. ± .5 e 17.69 Fe, 0.15% IAppendix, SI h opsto of composition The ± .2 o The Co. 0.02% oisS3– Movies ± 0.16% A and SI ihauiomcai retto.Vrain nteproportions the in Variations orientation. c-axis uniform a with of 6 regions (Fig. fine zone and cloudy 6 medium, the the coarse, (Fig. of the tetrataenite for one maps for orientation to orientation The corresponding c-axis of peaks choices superlattice three of set distinct a three anal- identifies angle Cluster recorded ysis postacquisition. the tilt unmixing in this statistical islands multiple requiring at of data, thickness overlap the lamella to effective leads inevitably The data. SPED of compo- tetrataenite 52 the observe be for we to Likewise zone, sition statistics). cloudy 52 counting medium X-ray at the in tetrataenite uncertainties as reflect of composition phases the zone 48 gives cloudy spectra average coarse the of quantification r hnaaye sn lse nlssshm,t isolate to scheme, (see analysis self-similar most cluster Methods). are a that regions using identify maps and analyzed processed The to then PCA. using approach dataset, data are Our the noise. dense denoising first and on statistically features relies sig- overlapping deconvolve a from to arising in strategies nals learning results machine applied pixel we pat- which every diffraction a at Recording phase. tern matrix ordered an distribution the identify the in to as out superstructure well map as to orientations nm, c-axis used tetrataenite 5 patterns, produce of diffraction experiments of SPED of sphere. series size Ewald a step the the of a increasing area and with recorded effects electron scattering recorded of dynamical minimizing be array while 2D to a patterns Zone. allows diffraction (SPED) Cloudy diffraction the electron sion of most Analysis the Crystallographic of with picture us provides chemical 3D-EDS accurate information. geometric whereas most accurate zone, the Ultimately, cloudy with methods. correspond the us quantification datasets provides the 3D-EDS in APT and uncertainties APT the both to Instead, in 5C). (Fig. variations regions fine the and significantly medium, change coarse, not the do between matrix and islands of compositions tal 85 at measured phase iisosurface. Ni a along planes Atomic Fe indicate dots ( Red Ni. in isosurface. are Ni dots 32.5% blue the atoms; showing zone cloudy fine the i.4. Fig. A omdi ealo h erteiepril ihihe in highlighted particle tetrataenite the of detail Zoomed-in (D) A. ± h110i %N,adtemti t84 at matrix the and Ni, 2% (A and ael a itdprle to parallel tilted was lamella P eosrcino w aaeso aenel from needle same of datasets two of reconstruction APT B) ± <100> h100i %F n 48 and Fe 2% C ± moholc rmtergo highlighted region the from othroslice nm 1 A ) D–F tet %F n 15 and Fe 2% a ersle nteitro fte32.5% the of interior the in resolved be can hwgop fnihoigislands neighboring of groups show ) ifato atrs ahcontaining each patterns, diffraction ± ± %F,16 Fe, 2% %N,wt h matrix the with Ni, 2% NSLts Articles Latest PNAS h100i ± %N.Teelemen- The Ni. 2% cnigpreces- Scanning o h collection the for ± %N (errors Ni 2% aeil and Materials ± %Fe, 2% | A–C). f10 of 3 C.

EARTH, ATMOSPHERIC, AND PLANETARY SCIENCES 90 cluster-based results) reveals that their relative positions change A Fe Upper APT B 80 Fe Lower APT as the beam position is rastered across the sample. While these Ni Upper APT 70 observations demonstrate unequivocally that the matrix phase is Ni Lower APT 60 an ordered structure, the precise nature of the ordered structure 50 is clearly more complex than the pure Fe3Ni structure proposed 40 by Bryson et al. (6). 30 Element (at%) 20 Micromagnetic State of the Cloudy Zone. Three neighboring 10 -4 -2 0 2 4 tetrataenite islands were extracted from the tomography stack C Distance from interface (nm) of the intermediate cloudy zone and converted to tetrahedral volume meshes (Fig. 8A). Two of the islands are approximately EDS Coarse EDS Intermediate prolate ellipsoids, with major axis diameters of ∼80 to 90 nm APT Fine and minor axis diameters of ∼40 to 50 nm. The third island is

Tetrataenite similar in size but has an L-shaped geometry (Fig. 3C), possibly resulting from a merger of two smaller islands. Finite-element micromagnetic simulations were performed initially using room- Matrix temperature micromagnetic parameters appropriate to cubic 0153045607590 3 Fe Concentration (at%) disordered Fe0.5Ni0.5 (Ms = 1,273 kA/m, K1 = 1 kJ/m , Aex = 1.13 ×10−11 J/m), which is a soft ferromagnet below its Curie Fig. 5. (A) Proxigrams for the two APT datasets in Fig. 4 A and B reveal temperature of ∼450 ◦C (18, 19). The matrix phase is not a sharp interface between the tetrataenite and matrix phases. (B) The included in the micromagnetic models, since Mossbauer¨ spec- thickness map-derived spectra for the two 3D-EDS studies presented. (C) troscopy demonstrates that the matrix phase is paramagnetic Comparison of Fe composition quantification results by APT and EDS for the tetrataenite and matrix phases. APT analyses revealed the average com- in the bulk cloudy zone (20, 21). All three islands adopted position of tetrataenite in the fine cloudy zone to be 48.4 ± 0.4% Fe to either single- or double-vortex states at remanence (Fig. 8B), 51.1 ± 0.4% Ni and the matrix phase in the fine region to be 81.8 ± 0.2% regardless of whether simulations were performed for each Fe and 17.8 ± 0.2% Ni. EDS quantification yielded a composition of 52.1 ± island separately or whether all three islands were simulated 2% Fe and 47.9 ± 2% Ni for the tetrataenite islands and 84.4 ± 2% Fe and together (including, thereby, the effects of magnetostatic inter- 15.6 ± 2% Ni for the matrix. actions between the islands). Magnetostatic interactions were sufficiently large to change significantly the values of vortex nucleation, switching, and annihilation fields during hysteresis of different easy axes in the cloudy zone are thought to reflect cycles and also to influence the sense of vortex rotation and the strength and direction of magnetic field present during cool- core magnetization adopted at remanence. The strength of inter- ing (see SI Appendix, Table S2). Due to the limited field of view, actions was not sufficient, however, to force the islands into a however, it is not possible to extract meaningful paleomagnetic single-domain state. “High-temperature” simulations were per- information from these data. Due to the projection thickness at formed by rescaling the micromagnetic parameters. Ms was this high tilt angle, a unique matrix diffraction pattern could not reduced by a factor of 2, Aex was reduced by a factor of 4, and be determined from this lamella. K1 was reduced to 0, corresponding to a normalized temperature To isolate the crystal structure of the matrix phase, a sec- of T/Tc = 0.9. The remanence states observed at room tem- ond lamella was fabricated with a surface normal approximately perature were all retained at high temperature, indicating that parallel to the [112] zone axis of the parent taenite crystal struc- above 320 ◦C (the critical temperature for Fe–Ni ordering in ture. In the field of view studied, we observed mainly [211] and tetrataenite) the cloudy zone can best be considered as an ensem- [121] orientations of tetrataenite islands, both of which lack ble of weakly to moderately interacting single- or double-vortex superlattice peaks associated with their ordered structure. In states. contrast, a superstructure in the matrix becomes apparent, lead- ing to a stronger overall diffraction condition, as seen in the STEM annular dark field image (Fig. 7A). Application of the cluster analysis of these SPED data reveals the presence of a diffraction pattern (Fig. 7C) unique to the matrix phase (Fig. 7B). The representative pattern contains strong reflections asso- ciated with the cubic lattice and additional superlattice reflec- tions, which arise due to the chemical ordering of the matrix phase. Bryson et al. (6) proposed an ordered matrix phase, based on the presence of superlattice peaks in [001] diffraction patterns collected from island/matrix regions containing only one or two out of the possible three tetrataenite orientations. When com- bined with EDS analysis, their observations were most consistent with a Fe3Ni cubic primitive structure. The (cluster center) diffraction pattern in Fig. 7C contains (110)¯ superlattice peaks that are consistent with such an ordering of the matrix phase  3 1¯ 1¯  (green spots in Fig. 7D). However, the presence of the 2 , 2 , 2 (purple spots in Fig. 7D) requires an additional doubling of the spacing of the (31¯1)¯ planes that is not consistent with the Fe3Ni Fig. 6. SPED cluster analysis results along the [001] direction of the cloudy structure. Furthermore, the arrows in Fig. 7C indicate that the zone. (A–C) The three dominant cluster centers for the three different {100}  ¯ ¯  3 , 1 , 1 and (110) superlattice peaks are not exactly aligned. tetrataenite orientations. (D–F) Cluster loading maps, showing how the 2 2 2 three different orientations group in the (D) coarse, (E) intermediate, and Close examination of these peaks (in both the raw data and (F) fine regions of the cloudy zone.

4 of 10 | www.pnas.org/cgi/doi/10.1073/pnas.1809378115 Einsle et al. Downloaded by guest on September 26, 2021 Downloaded by guest on September 26, 2021 edcue al odslc n vnulyanhlt tthe at annihilate eventually and ten- displace interaction greater to the a as walls adopted, was caused be there to field states however, single-domain for included, a dency between were by interactions islands separated magnetostatic the When domains of wall. magnetized consisting domain state, oppositely central two-domain and a equal of single-domain short formation two or stable the long intermediate a to the the to either leads along transition axes along axis a easy axis to the For Placing leads easy state. 6). island uniaxial (Fig. the SPED of the axis using placing observed ori- islands, c-axis was isolated equal islands clusters with three small the islands all mimicking of of thereby of direction, c-axis axis same the the short in islands, ented or three cho- of intermediate, cluster was long, a axis the (see easy either islands uniaxial along the the lie of to orientation throughout sen ordering The Fe–Ni system. in the increase anisotropy of homogeneous increments uniaxial and in uous the (22)] tetrataenite kJ/m which pure 10 for in value simulations temperature from of increased series was a in highlighted boundary antiphase green. an in with Fe [112] (E the of down results. simulations viewed experimental when kinematic on phase based with structure. added line ordered are in spots proposed are ple Schematic the spots (D) on green arrows. and based Black black [112] and along white pattern diffraction with highlighted reflections latice isee al. et Einsle pattern diffraction center cluster Cluster the in (B) with shown matrix. associated Fe-rich map bright loading the analysis against dark are particles Tetrataenite 7. Fig. h feto eN reigblw320 below ordering Fe–Ni of effect The TMHAFo luyzn ln h 12 direction. [112] the along zone cloudy of STEM-HAADF (A) 3 (C C. hspoeueapoiae h feto contin- a of effect the approximates procedure This . lse etrfrtemti hs.Mslgmn fsuper- of Misalignment phase. matrix the for center Cluster ) IAppendix, SI K u to 0 = .We simulating When S6–S9). Movies K u 30kJ/m 1370 = oe o h matrix the for Model ) ◦ a explored was C 3 teroom- [the 3 i Pur- Ni. eoeadatrtetasto (see obvious transition no remanence the is of there after direction system; or and intensity the before the of rearrange- two-domain either state between complete to magnetic relation a vortex the The of represents ment 8C). transition (Fig. single-domain islands to the of boundary and aeta hr sapeeec o h lnaindrcino an of direction the elongation of the one for with specu- align preference We to shape a island islands. the is tetrataenite of there that the control late of crystallographic direction is elongation there pro- and that as hint classified first average, weak the on A are, but ellipsoids. a shapes have late and sim- islands sizes Intermediate be matrix, of process. also coarsening range may of the but of regions relics precipitates, ple secondary isolated like more inter- appear particles which contain two islands of composed tetrataenite be 90 parti- to at Tetrataenite observed secting the S13 ). often while Fig. are , Appendix coarsening cles (SI of cooled process islands body the smaller parent during as as threads trapped coalesced of became and network that grew this material interpret matrix on We of matrix island. relics main an the to of back side connects either mate- that matrix network fine-scale a of forming rial, threads cloudy multiple coarse the contain In islands zones. zone, cloudy fine and intermediate, coarse, rate, phase cooling low-temperature the the of con- on matrix, (2). function based Fe-rich diagram more expectations a a with to is compo- leading sistent phase the rates cooling more that matrix slower a suggests with the examined This who of (26), meteorite. contrast sition al. examined IVA et results who Rout cooled Our of (27), rapidly history. results al. APT cooling the et similar with Miller a use into of with data the work meteorites composition through the our phase with brings each agreement This APT. from high-resolution signals of of enhanced isolate methods the to sophisticated with combined more capability here, the used by quantification explained 3D-EDS previous the is some that analysis Fe proposal in cal ordered the suggested pure with inconsistent be is been and matrix to has 23–26) revealed than 6, is (2, Fe studies matrix in the How- chemistry richer expected. of as The much composition tetrataenite, chemical zone. with the cloudy consistent ever, fine is tem- islands the the the to of down of formation least at of maintained gradient. was perature between chemical matrix equilibrium and wide) chemical two islands nm the the the that (<2 with implies sharp observation zone, Ni a This cloudy Fe:17.7% by entire 82.0% separated the matrix phases throughout and Ni, observed Fe:50.0% simple are rather 49.6% a the at for Chemically, comprehensive islands compositions date. constant most and to the Well-defined zone emerges: yielded picture cloudy has the APT of and picture Zone. Cloudy TEM of of State nation and Structural and Chemical The Discussion sn PE.Tecoemthbtentesaeadsz of size and shape the the between the meteorite explain match Tazewell close in to the The observed of (7) XPEEM. zone domains using al. cloudy magnetic intermediate et and of Bryson coarse size by large Clus- predicted orientation. unexpectedly first c-axis of uniform was consists with but islands tering random of clusters not distribu- nm is 500 The orientations zone. c-axis cloudy assumptions of orienta- the fundamental tion of c-axis the studies of different nanopaleomagnetic one of adopt confirming to thereby able tions, are islands sec- tetrataenite any, if undergone few, has show zone fine coarsening. zone the less c-axis fine that the indicating the to precipitates, in parallel ondary Islands is direction tetrataenite. elongation of this that and phase opooial,w bev itntcaatrsisi the in characteristics distinct observe we Morphologically, rsalgahcly ehv eosrtdta nearby that demonstrated have we Crystallographically, S11 ). ◦ .I h nemdaecod zone, cloudy intermediate the In 3C). and 1 (Figs. {100} 3 i() h mrvmn nchemi- in improvement The (6). 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EARTH, ATMOSPHERIC, AND PLANETARY SCIENCES the c-axis clusters observed with SPED and the shape and size of magnetic domains observed with XPEEM confirms that the magnetic state of the cloudy zone is controlled by the under- lying crystallography and clustering of the islands. This is most evident in the fine zone, which typically displays a strong and uni- form magnetization with localized deviations in magnetization direction causing a fine-scale mottling in both electron holog- raphy and XPEEM images. A high degree of c-axis alignment is required to explain these observations. The origin of this enhanced c-axis alignment in not well understood, but various possibilities are considered below. The electron diffraction pattern for the matrix phase (Fig. 7) contains two distinct sets of superlattice reflections. The first set of reflections (110 type; green spots in Fig. 7D) are consistent with one of the three possible tetrataenite orientations as well as Fe3Ni when viewed along the [112]. The application of data clustering to the scanning diffraction data, however, spatially localizes this diffraction pattern to the matrix region. Addition- ally, the cluster center presented in Fig. 7C contains a second set of reflections that are incompatible with either Fe3Ni or tetrataenite (pink spots in Fig. 7D). These reflections require a further doubling of the lattice periodicity. Although such a dou- bling could, in principle, be explained by an ordered structure of the Fe7Ni type, this structure does not provide a good fit to the intensities of superlattice peaks, nor does it explain the obser- vation that the row of superlattice spots are clearly misaligned with respect to each other. We propose an alternative model, whereby the approximate doubling of lattice periodicity occurs inside antiphase boundaries created by incommensurate order- ing of Fe and Ni (Fig. 7E). Local doubling of the periodicity of (31¯1)¯ planes occurs within the antiphase boundary regions. The presence of antiphase boundaries also provides a mechanism for short-range chemical segregation, enabling the incorporation of additional Fe into the structure needed to match the experimen- tally observed composition of the matrix (note that excess Fe is found in the central part of the kinked antiphase boundary in Fig. 7E). Such incommensurate ordering, creating high densi- ties of antiphase boundaries and local chemical segregation, is well known in off-stoichiometry A3B alloys (28, 29), which create similar patterns of superlattice reflections. Conventional Fe–Ni systems in this composition range usually undergo a martensitic transformation upon cooling. However, it appears that, in this case, the high degree of lattice coherency within the intergrowth, and the relatively small volume of the matrix phase, provides a sufficiently large barrier to this transformation, allowing the newly identified ordered phase to exist metastably. Compositionally, the matrix lies in between Fe3Ni and Fe7Ni. The magnetic ground state of Fe3Ni is predicted to be ferromag- netic at 0 K, with a moment of 2.066 µB per atom (compared with the 2.2 µB per atom for Fe in kamacite) (30). The mag- netic ground state of Fe7Ni is predicted to be ferrimagnetic with a moment of 0.942 µB (30). We can speculate that the mag- netic ground state of the matrix lies somewhere between these two cases. The matrix is paramagnetic at room temperature due to its combination of high Fe content and fcc structure, which is incompatible with strong ferromagnetism (31). This property matches the proposed properties of antitaenite, a low-moment Fig. 8. (A) Finite-element meshes of three neighboring islands extracted phase of taenite that is the most widely accepted explanation from the 3D-EDS tomography reconstruction of the intermediate cloudy for the matrix phase. It is tempting, therefore, to state that anti- zone. Average mesh element size is 1.6 nm. Best-fitting ellipsoids yield taenite and the Fe-enriched, incommensurate ordered structure island sizes of (red) 82 × 48 × 38 nm, (white) 92 × 61 × 40 nm, and (blue) identified here are one and the same thing, although this state- 92 × 47 × 41 nm. The white island has a distinct L shape due to coalescence ment would have to be corroborated by further studies involving of two smaller islands. (B) Remanent micromagnetic state for interacting a wider range of Fe–Ni meteorites. islands of taenite, representing the likely magnetic state of the cloudy zone above 320 ◦C. Islands adopt predominantly single (occasionally double) vor- tex states. Green isosurfaces outline the approximate position of the vortex core. (C) Remanent micromagnetic state for interacting islands of tetrataen- the red island in A. Two islands show ideal single-domain states. The ite, representing the likely magnetic state of the cloudy zone below 320 ◦C. third island adopts a two-domain state with a sharp domain wall at the The tetrataenite easy axis for all three islands is parallel to the long axis of intersection of the two coalesced islands.

6 of 10 | www.pnas.org/cgi/doi/10.1073/pnas.1809378115 Einsle et al. Downloaded by guest on September 26, 2021 Downloaded by guest on September 26, 2021 luyzn dpsvre ttsfrT for states vortex intermediate adopts to coarse zone the that cloudy demonstrated Zone. Cloudy have the we in netically, Acquisition Remanence of Mechanism The isee al. et Einsle (9) al. et stands. Nichols still by Esquel extended respectively, subsequently body, and solid- was parent core approach Imilac of pallasite Their stages the the observation late on in and al.’s ification early magnetization et the weak Bryson representing meteorites, reason, and 320 this strong to For sev- cooled of that studying rates. body by different parent derived single at be a still from meteorites can the eral activity time-resolved of times, dynamo subregions different of sequential at records which remanence in postu- record (7), While originally zone al. as cloudy content. et resolution Ni Bryson time by local of lated concept the sequen- the to at destroys than according this rather their times time, record in different regions instance tially same all the then at decomposition, remanence spinodal of If 320 at ature zone. recorded cloudy paleo- is the remanence time-resolved all throughout of recorded concept may information the magnetic that for 320 remanence implications above of pro- recorded profound ordering memory been this have any during already erasing recorded suggesting potentially is tetrataenite, remanence to cess, transition final the the of that result a as matically meteorite the on present the field body. and magnetic parent state ancient remanence the quan- of final the intensity larger the investigating between much also relationship include and titative to islands simulations interacting be of the to numbers extending likely as complex- inter- these such explore is magnetostatic to ities, needed islands now of is work influence magnetized Further dominant. zone. the uniformly cloudy zone, between the cloudy actions in fine magnetization the the domain secondary explaining In high of remagnetization, the lack wall, prevents apparent domain field move- is the nucleation the remanence of wall the Once biasing annihilation transition. influence by the by during to zone blocked, walls field cloudy domain of the ancient ment of an state for provides paleomagnetic mechanism tetrataenite, by single- to effective driven a taenite state, an from to two-domain transformation vor- single-vortex latter. intermediate phase of a the an the in via from presence states state, transition the single-domain domain state by and domain former caused the The zone, in cloudy states rema- zones tex fine of cloudy mechanism coarse/intermediate the the the versus within in the acquisition difference from nence fundamental We different (32). a models very previous predict in is rema- is envisaged paleomagnetic blocking process this blocking of of thermal is, acquisition mechanism annihilates—that the This This wall for nence. T). point domain 1 blocking the of the order once effec- the becomes fixed island (of each tively of high a state very magnetization Once the is that domain. renu- means wall to single domain needed bound- field a the the island cleate produce achieved, the been to has to state annihilates magnetostatic displace single-domain it important to as where wall an well domain ary, plays as the islands, causing field, pres- role, neighboring at applied the between or externally However, interactions island an islands. the be coalescing of to two of ence chosen of direction is intersection elongation c-axis the the the when to islands perpendicular isolated single-domain in state to preserved two-domain uni- A vortex is state. in two-domain from intermediate increase transition an see dramatic via a states, a 2:1; and to ratio anisotropy leads aspect axial tetrataenite with form 320 to ellipsoid will Below atoms prolate Methods ). states a 65 and particles; vortex for Materials spherical axis so for long diameter single- state, nm nm the than (22.5 domain larger threshold islands their domain containing regions on islands all in effect taenite dominate between no interactions have magnetostatic moderate ohteitniyaddrcino eaec hnedra- change remanence of direction and intensity the Both ◦ ,rte hna h temper- the at than rather C, ◦ ,odrn fF n Ni and Fe of ordering C, ◦ .Ti ttmn has statement This C. > 320 ◦ .Wa to Weak C. Mag- ◦ C ul sltdilnso igedmi erteie ihhighly with tetrataenite, single-domain optimal of these islands that where isolated suggest intergrowth, (6, two-phase study fully zone a present through cloudy achieved the are fine of conditions the results in holog- The electron measurements 7). using XPEEM observed and are and which raphy magnetization of saturation both it the coercivity, both product, the maximize energy permanent to maximum sustainable necessary the is a achieve cloudy for To optimize fine template material. The to magnetic suitable 33). strive a scope (3, we provides tetrataenite a as zone synthetic is nature of there from properties that lessons the suggesting valuable zone, learn mag- regions cloudy to localized earth meteorite in rare coercivity the to higher of much competitor observe viable below We is a (3). far nets become so to produced needed material the that Unfortunately, creat- of use. coercivity of industrial magnetic possibility for the the tetrataenite up synthetic bulk opening (i.e., ing (4), short on scales tetrataenite time well-ordered laboratory) of pro- quantities to gram developed been duce and has process insertion (NITE) nitrogen extraction topotactic low-temperature be a to need Recently, alternatives renewable developed. sustainable and that transport means the industries, increasing in energy the magnets with permanent combined impact for of elements, demand environmental earth range and rare wide extracting scarcity of a the possess However, magnets applications. permanent rare-earth Magnets. Permanent thetic Earth-Free of Rare Sustainable process to Pathway a A through alignment of degree high self-organization. conditions, the these under to enhanced leading dramatically ori- be c-axis may of choice entation the influence ability to The interactions field. magnetostatic stability of tetrataenite the 320 within already below grow initiate will used will decomposition commonly regions spinodal these (2), most system in the Fe–Ni low- the to for with According diagram regions phase content. in Ni form average islands est finest tetrataenite the to taenite Second, chances of the transition). the through degrees increase inherited being higher above, remanence suggested cause of as may (and, alignment which c-axis magne- 320 fields, larger below generate interaction and will tostatic magnetization above uniform states, both with vortex dominate cloudy islands than to fine rather the likely states, in are single-domain islands that Smaller mean magnetostatic alignment. zone mechanism strong matrix, alternative to an paramagnetic leading provide a islands With between (21). interactions and surfaces films at ferromagnetic thin appears in only paramagnetic and is phase matrix bulk the the in that being shown phase M since matrix have High-resolution the measurements between 7). on coupling contingent (6, exchange are ferromagnetic matrix to the due via was islands sug- effect Previous this origins. possible that several gestions Cloudy have may Fine zone the cloudy in fine Properties Magnetic Hard Zone. Optimal of Origin The evi- preserve parent their which by generated meteorites, (10). example, field body magnetic for IVA time-varying apply, a cooled of would dence rapidly case some This be island. to to in taenite magnetization likely uniform parent is of c-axis the direction tetrataenite the of by to choice influenced transition the strongly the since a during remanence, retain preexisting orientation to capacity a the of enhanced memory significantly thresh- have single-domain may the size below old the islands of containing regions zone addition, cloudy In a preex- preserving record. of thereby paleomagnetic fraction transition, time-resolved the any survive whether can remanence determine islands isting to interacting necessary of Simu- now ensembles solidification. are larger core much preceded containing on that activity lations body dynamo parent of pallise period quiescent the predicted the observe to h ihdge fmgei lgmn bevdi the in observed alignment magnetic of degree high The ◦ NSLts Articles Latest PNAS ,i hc aeislands case which in C, sburspectroscopy ossbauer ¨ ◦ .Taenite C. | f10 of 7 Syn-

EARTH, ATMOSPHERIC, AND PLANETARY SCIENCES aligned c-axes, are coherently intergrown with a metastable, par- transform in Sci-Kit Image (Python), giving a phase-specific thickness map at tially ordered fcc paramagnetic matrix phase. Adapting the NITE each tilt angle (40, 41). These thickness maps were registered to the raw EDS process to produce a synthetic equivalent of the ordered matrix spectra using image-processing routines in Matlab. The reconstruction prob- phase may be achievable by simple modification of the chemi- lem was then recast as a system of linear equations, assuming the observed cal composition of the precursor Fe–Ni alloy. Mechanical mixing spectra were a linear combination of signals arising from the island and matrix phases. At each energy channel, the 348,000 simultaneous equations of synthetic tetrataenite and matrix nanoparticles, followed by provided for an overdetermined problem to recover the coefficients cor- low-temperature/high-pressure sintering in the presence of a responding to the intensity at each energy channel for each of the two strong magnetic field, would then provide a potential route to phases. Across the entire spectrum, this analysis determined the character- fabricating the same two-phase nanocomposite of tetrataenite istic EDS spectra of the island and matrix phases based on the physically and matrix phase in the laboratory that nature took tens of segmented tomography volume (Fig. 3A). Cliff–Lorimer methods were used millions of years to achieve on the meteorite parent body. to quantify the Fe–Ni ratio from the resulting EDS spectra. We estimate the relative uncertainty in the ratio to be at 2% based on counting statistics. Materials and Methods Errors associated with the first principles-derived k-factors provided by the instrument manufacturer have been reported at approximately 8% using Sample Preparation. A section of the Tazewell meteorite was acquired the Co-K and Pt-L lines (42). However, calculated Fe and Ni k-factors for K from the Sedgwick Museum of Earth Sciences, University of Cambridge, lines are known to have particularly low errors (1% to 2%) (43) and are sys- sample no. 16269. The same sample has previously been studied using tematic and of similar small magnitudes for Fe and Ni (and will therefore be electron holography, XPEEM, and Mossbauer¨ spectroscopy. Focused Ion substantially reduced in relative composition). As such, we report 2% errors Beam (FIB) milling with in situ lift-out was used to prepare samples for for EDS quantification in line with the X-ray counting statistics. SPED, 3D-EDS, and APT study, using an FEI Helios Dual-Beam FIB located in the Department of Materials Science and Metallurgy, University of Cam- APT. APT experiments were carried out on a LEAP 3000X-HR instrument bridge. Planar lamellae were prepared for SPED analysis using a basic (University of Oxford), running in laser mode with a 532 nm beam oper- in situ TEM lamella preparation strategy. Final thinning and low kilovolt ating at 0.4 nJ. A small subset of samples were also run in voltage mode, cleaning were performed using a simplified version of the process out- to confirm the accuracy of composition data, although the data yield was lined by Schaffer et al. (34). Tomography needle samples were fabricated lower from these. The specimen stage temperature was kept at 55 K for using the block lift-out approach described by Thompson et al. (35). For all experiments. Data were reconstructed using IVAS software (3.6.12). The 3D-EDS and APT studies, blocks of the cloudy zone were lifted out and composition of the islands and matrix was obtained by placing numerous mounted in situ onto tomography posts. For 3D-EDS, Cu tomography pins cylindrical regions of interest at least 1 nm away from the nearest inter- specifically designed to work with the Fischione Instruments 2050 full- face, in order avoid sampling neighboring phases (SI Appendix, Fig. S3). tilt tomography sample holder were used. APT needles were mounted on The atoms inside multiple cylinders across multiple datasets were summed a Cameca silicon lift-out coupon with 36 posts. After welding with FIB- to produce the average compositions quoted. The compositional varia- induced Pt deposition, needle geometries were formed using the procedure + tions of either phase between different APT datasets were not statistically described by Larson et al. (36). Amorphous damage and Ga implantation significant. were removed using a 2 kV, 100 pA polishing step. Several APT samples were fabricated with the tip axis parallel to either the [001] and [110] SPED. SPED allows for detailed crystallographic mapping of a sample by directions. precessing the electron beam about a small angle. This results in diffrac- tion patterns where the dynamical effects of scattering are minimized and 3D-EDS. Tomographic elemental mapping of the cloudy zone was per- we are able to record a larger region of the Ewald sphere (44). Here, the formed using EDS on an FEI Tecnai Osiris 80-200, operating at an acceler- electron probe is also scanned across the region of interest to map out the ating voltage of 200 kV. The high density of the Fe–Ni phase in the cloudy crystallography of the sample. We use a Phillips CM300 FEGTEM equipped zone coupled with the variable thickness of a tomography needle geome- with a Nanomegas ASTAR precession system. Using 300 kV spot 7, we col- try means that electron energy loss spectroscopy would suffer from multiple lect diffraction patterns every 5 nm in the region of interest. For the sample scattering events, leading to nonquantitative results. Additionally, the four- oriented along the [100] direction, we collected three sets of maps, one detector geometry of the Osiris instrument allows for rapid mapping of the from the coarse, medium, and fine regions of the cloudy zone (Fig. 6). Each sample, minimizing drift during the tilt series collection. Needle samples [100] map collected was 600 nm × 600 nm. For the lamella oriented along were loaded into the microscope using the Fischione full-tilt tomography the [112] zone axis of the parent taenite crystal structure, a single map of ◦ ◦ ◦ holder. The EDS tilt series was collected every 5 from −70 to +75 . Ele- 220 nm × 235 nm was collected (Fig. 7). Once the data were collected, the mental maps were collected in a 246 nm × 327 nm region of interest on maps were then analyzed using cluster analysis, to determine the dominant each of the tomography needles studied. With a pixel size of 2.46 nm, this diffraction patterns (45). This allows for physical diffraction patterns to be resulted in the collection of 348,000 spectra. analyzed and orientation maps to be produced.

EDS Structural and Chemical Quantification. The EDS tilt series collected pro- Cluster Analysis. Cluster analysis is the unsupervised (or semisupervised) duces a statistically dense spectral dataset. Integrated Fe and Ni spectral identification and classification of groups of points that lie close together peak intensities were extracted from the EDS tilt series using spectral and in space (46). In the context of SPED, for a highly coherent crystal struc- machine-learning tools in the open source Python library, Hyperspy (37). ture such as that reported here, statistical decomposition methods such The spectra were denoised using PCA and background-subtracted before as PCA and Nonnegative Matrix Factorization (NMF) can be misleading, performing the intensity integration on the two respective elemental peaks. because so many of the reflections are common to all of the diffrac- Intensity integration produces a grayscale tilt series for each element, where tion patterns in the scan. As a result, the common reflections tend to be the peak intensity is proportional to the quantity of iron or nickel present grouped into one significant component and variations in the structure in each pixel. The tilt series are aligned using TomoJ (38) and then recon- (often limited to a small number of weak reflections) are associated with structed using an in-house CS algorithm (14, 15). The two resulting volumes the higher components. For clustering, each diffraction pattern is assigned were individually segmented using a random walker algorithm (39), and the a position in high-dimensional space according to how much of each com- resulting volumes were then compared with the structural morphologies for ponent is associated with it. Clusters are formed by grouping points in tetrataenite and matrix phases seen in Figs. 2 and 3. Morphological analy- this space that are “close together,” and the average diffraction pattern sis was performed on the segmented Ni maps, as these provided a stronger for each signal is calculated from that point in space. Although it is com- contrast between tetrataenite particles and the Fe3Ni matrix. mon to define distances using a Euclidean metric, custom metrics can be CS reconstruction preserves the boundaries and physical morphologies used as well. The key advantage here is that the component corresponding of features found in the tilt series. However, the resulting grayscale values to the common reflections can and will be included in the cluster rep- in the reconstruction are not linearly preserved. This results in uncertainty resentations, leading to meaningful diffraction patterns that nevertheless for the use of the reconstructed grayscale information for EDS quantifica- highlight the key structural differences between the different phases in the tion. We addressed this uncertainty by developing an alternative method for microstructure. the quantification of 3D chemical data. First, the CS reconstruction volume For Fig. 7, initial decomposition was performed using NMF retaining 6 was segmented to label voxels as either Ni-rich or Fe-rich. These chemical components. Clustering was performed using the Gustafson–Kessel varia- phase-specific subvolumes were then reprojected, using a discrete Radon tion of the probabilistic fuzzy c-means algorithm, searching for five clusters

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H, Leroux J, nitrogen Gattacceca by M, powder magnet Uehara L10-FeNi single-phase 5. of Synthesis (2017) permanent al. for et tetrataenite S, Investigating Goto nature: by 4. Inspired (2014) al. et decomposition LH, phase Lewis Low-temperature 3. (1997) J Goldstein D, Williams CW, on Yang fields 2. 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N 22. h omtmeaueprmtr eestrto magnetization with saturation constant were exchange kA/m, parameters 1,390 temperature room the rde ...adBHM cnweg nnilspotfo h Royal the from support financial Cam- acknowledge College, B.H.M. Society. Girton and P.A.M. and A.S.E. Fellowship and bridge. Research S.M.C. Henslow 291522-3DIMAGE. S.M.C. the Grant Advanced acknowledges 320750-Nanopaleomagnetism. ERC under funding Grant acknowledge Advanced ERC ACKNOWLEDGMENTS. decreasing-size loop. the hysteresis during size 0.1. obtained the limit of cal- of lower 50 portion was steps the diameter 2:1 are in of values ratio again Quoted mesh aspect size. back with with initial and particle used, an ellipsoid 3 was using prolate size culated to a element 0.5 A for nm 47. from threshold 1 ref. The varying and of factors diameter method scaling nm size-scaling size 25 the next par- of using the spherical mesh calculated for a spherical was configuration for taenite starting threshold of the single-domain ticle as room-temperature used The was step. step increased each was at anisotropy the solution uniaxial tetrataenite, the to and zero taenite from to from one set transition just was for the anisotropy found simulate cubic axis To short islands. to or set intermediate, the was long, of simulations the vector either anisotropy For to the island. parallel islands, each be interacting for three ellipsoid all best-fit intermediate, on the long, performed for the found either to axis parallel short be or to set was vector anisotropy the nertdeeto ifato intensities. diffraction electron integrated microscope. electron transmission scanning C410. Kv 200 H700h approach. section cross partial a using nanoparticles nano-catalysts ceria lanthanum-doped microscopy. in electron 3D hybridization by orbital revealed and chemistry face TEM. from SrTiO3 of surface Intell microscopy. electron transmission Bioinformatics in reconstruction three-dimensional for ware Ultramicroscopy tomography. FIB. by voltages low at STEM 5:16627. specimens. rock 121:15–26. small from reconstruction field omagnetic Ni. 20-40% approximately at state equilibrium eN-ern eerts ptxa negot of intergrowth Epitaxial meteorites: Fe-Ni-bearing 53:4029–4041. simulations. atomistic and calculations first-principles by Investigation structure. domain lcrndfrcinstudy. diffraction Electron meteorites. meteorite. Catharina Santa iron and City IVA Twin the Bristol in fast-cooled the in Sci interface Planet Meteorit kamacite-taenite the of meteorites. stony-iron and iron of 52:617–626. phases metallic the in origin. and bodies, parent histories. thermal their for Implications chondrites: bombardment. neutron by ordered 876. crystal single iron-nickel an e ,PueeJ atee ,LuirJ atep 16)Mgei rprisof properties Magnetic (1964) D Dautreppe J, Laugier R, Pauthenet J, Pauleve L, eel ´ K K u u 28:1768–1783. ,7 kJ/m 1,370 = to 0 = aF ta.(07 yeSy eso 1.1.2. Version HyperSpy, (2017) al. et F, na ˜ Ultramicroscopy K 8:288. u 79:287–293. hsScJpn Soc Phys J ,7 kJ/m 1,370 = 52:2707–2729. 3 2) o iuain efre nidvda islands, individual on performed simulations For (22)...... adRJH cnweg udn under funding acknowledge R.J.H. and P.A.M. J.F.E., hsScJpn Soc Phys J hmErde Chem Nature Ultramicroscopy 107:131–139. 12:7–13. A 3 ex niceet f1 kJ/m 10 of increments in 490:384–387. c Rep Sci 1.13 = 69:293–325. 11:226–239. γ Ultramicroscopy -Fe-Ni(γ 7:5406. ×10 114:62–71. anMg Mater Magn Magn J hsColloq Phys J 10.5281/ZENODO.240660. Zenodo, −11 NSLts Articles Latest PNAS × γ S rpsda e iea in mineral new a as proposed LS) eertPae Sci Planet Meteorit Sadttaant sapossible a as tetrataenite and LS irs Microanal Microsc 5n n melement nm 1 and nm 25 EETasPtenAa Mach Anal Pattern Trans IEEE /,adcbcanisotropy cubic and J/m, eci omci Acta Cosmochim Geochim epy e oi Earth Solid Res Geophys J 53:271–282. hsColloq Phys J 50:413–418. 3 plPhys Appl J h converged The . 150:30–36. caMaterialia Acta 35:569–580. 22:71–81. | 45:C407– 35:873– f10 of 9 c Rep Sci M BMC s =

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