National Bureau of Standards Reference book v, K.W. Bldg not to be taken from OCT 8 1964 the library. ^ecknical ^iot& 247 SURVEY OF MAGNETIC THIN FILM MATERIALS GEORGE W. REIMHERR W5^V.,^S»«¥1 U. S. DEPARTMENT OF COMMERCE NATIONAL BUREAU OF STANDARDS THE NATIONAL BUREAU OF STANDARDS The National Bureau of Standards is a principal focal point in the Federal Government for assuring maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. 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Office of Technical Services. Office of Weights and Measures. Office of Engineer- ing Standards. Office of Industrial Services. * NBS Group, Joint Institute for Laboratory Astrophysics at the University of Colorado. ** Located at Boulder, Colorado. NATIONAL BUREAU OF STANDARDS Technical Note 247 ISSUED SEPTEMBER 25, 1964 SURVEY OF MAGNETIC THIN FILM MATERIALS George W. Reimherr NBS Technical Notes are designed to supplement the Bu- reau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be listed or referred to in the open literature. For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C., 20402 Price A Survey of Magnetic Thin Film Materials by- George William Reimherr This survey lists the materials reportedly made as a magnetic thin film, along with some of their properties and potential applications . Research activity using the less -frequently mentioned magnetic film materials is noted. About 200 references are cited. 1. Introduction The growth of activity in magnetic thin film research is indicated by the increasing number of papers published in this field. For example, the Magnetic Materials Digest series zJ lists 26 papers in 1958, 33 in 1959, 70 in I960, 131 in 1961, and at least 180 papers in 1962 that concern magnetic thin films. Much of this activity, both for research and for practical applications, has been with the nonmagneto- strictive 8lNi-19Fe permalloy composition. However, a sizable activity has concerned other compositions, particularly as fabrication techniques become better known. This survey lists some of the properties, interesting features, and proposed applications of the various magnetic film materials. Research activity with theTesser -mentioned magnetic film materials is included. 2. Structure and Magnetic Properties of Materials Reported as a Magnetic Thin Film The Key to Table I The following items represent the various column headings of Table I, in the order of their appearance. All values (except Curie temperature) are given for about 20° C. 1/ References (100) through (103). 1. Materials. These are the materials reportedly made in the form of a magnetic thin film. In a few cases, the source composition rather than the film composition is given; these cases are noted by the words "source composition. " - Magnetic films are prepared by a variety of techniques, including vacuum evaporation, electrodeposition, electroless deposition, and sputtering. Substrates are generally of glass or of metal such as aluminum, copper, gold, etc. , although such materials as mica, MgO, NaCl, etc. , are also used. 2. Structure. The structure type is listed, along with the lattice constants (a, c). 3. Curie temperature. Units are in degrees Celsius ( C). 4. M s . This is the saturation magnetization, defined (in the cgs-emu system) as B - H for very large H. 5. Hc . This is the coercive force reported for the material as a magnetic thin film. Specific examples are sometimes given in cases where a typical range of values is not readily available 6. Hfc. This is the anisotropy field of the film. (See remarks for Hc , above. ) A few materials have no magnetic anisotropy and are therefore listed as isotropic. 7. Ki. This is the crystalline anisotropy constant of the material. 8. Xs« This represents the saturation magnetostriction of the polycrystalline material. 9. References. The reference sources are listed in paren- theses (1) ... (201). The selected bibliography appears at the back. 3. o Other Abbreviations 1. A Angstrom unit 2. (b) value measured on. bulk material }J 3. bcc body centered cubic 4. cc cubic centimeter 5. (f) value measured on film material f/ 6. fee face centered cubic 7. hep hexagonal close packed 8. hex hexagonal 9. Hw wall coercive force 10. oe. oersteds 11. ref reference 12. temp temperature 13. wt. weight 14. fisec. microseconds 15. r*-t about, approximately y In Table I, values given for the lattice constants, Curie temperature, and M s , were generally measured on the bulk material; values for Ki and \ s were measured on bulk (b) or on film (f), while values of H c and H^ were measured on the film material. Values measured on the bulk material for the lattice constants, Curie temperature, M s , K}, and X&, are generally considered applicable to the thin film a l^,o_3/ except possibly for the ultra-thin film --- ~ < 30 A thick). However, values given for Hc and for H^ are unique to the thin film, because of their strong dependence on how the film is made. U Although this has not been verified in every case. Table I. Structure and Magnetic Properties of Materials Reported as a Magnetic Thin Film Note to Accompany Table 1 To convert the given cgs-emu values to the International System (SI), (1) Multiply the number of oersteds by 79- 58 ( = 1000/4tt) to express H in amperes per meter, (2) Multiply the value of the 10 magnetization in gauss by 0. 001257 ( = 4ir "^ to obtain the magnetic polarization (intrinsic induction) in teslas. : Material Structure Curie Temp. Ms Hk Kl *s CO (gauss) (oe.) (oe.) (ergs/cc) la 5 6 Iron - bee bee 770 1714 values +4.5xl0 -7xl0" (1) (1) from (f) (6) (7) a = 2.861 A ~10 5 (8) (3) (3) (4) +4.6xl0 (1) up to (b) (2) several (3) 5 hundred +4.9+0.1xl0 (5) (f) (4) see comments also lb Iron - fee fee Neel see comments o temp. a = 3.588 A uncertain; at room see temp. (9) comments 2a 4 6 Nickel fee 358 484.1 10 to 35 example: -3.6xl0 to -34xl0" (1) (1) (ID 4 to 12 4 (7) (fee) a = 3.517 A -4.5xl0 (3) (3) (13) (8) (2) another (f) (6) . o (16) ref: (12), 4 a = 3.524 A -4.6xl0 (10) Fig. 6 (f) (14) 4 -5.5xl0 (b) (15) 2b Nickel hep (hep) a = 2.66 A see comments c = 4.29 A (2) 3a 6 6 Cobalt hep phase 1422 examples 5.3xl0 -70xlO" change (3) (b) (3) (b) (3) (hep) a = 2.514 A 35 (17) occurs general ref. for c = 4.105 A below 40 (18) ref. for polycrys. (2) Curie bulk: cobalt: temp. (19) (20) 3b Cobalt fee 1130 (-1420) ref. for see (1) bulk: (19) comments (fee) . a = 3.554 A ref. for (2) 1131 temp, ref. for above films: a = 3.56± (3) 500° C: see 0.01 A (19) comments (21) . : ) Material Structure Curie Temp. H Ms c Hk Kl ^s (°C) (gauss) (oe.) (oe.) (ergs/cc) 4 Gadolinium hep 16 ref. (25) some (1) a = 3.622 A (paramag- (b) mention (3) netic at in ref. c = 5.748 A (26) 17 room tern] >.) (22) (23) (24) 5 6 6 MnBi hex. 360 620 high, _-__ 9.1xl0 800xl0~ o probably a = 4.287 A (3) (3) (27) (27) (27) several other other c = 6.126 A thousand; ref.: ref.: (27) see sec- tion on (28) (28) magnetic thin film papers 6a 3 81Ni-19Fe fee <~585 ~ 800 0.5 to 5.0; 2.5 to -1.6xl0 nearly (1) (1) typically 5.0; (f) nonmag- a = 3.54 A (6) 0.5H to typically neto- (1) k 0.9Hk ~3. stric- (29) (29) tive alloy (b) ; (f (29) 6b 3 -6 50Ni-50Fe fee — 500 — 1270 example .... 33xl0" r^26xl0 o ~10 a~3.58 A (3) (1) to 20 (b) (1) (30) (3) for 45% (1) (30) permalloy films (18) 6c 3Ni-97Fe bee ~770 ~1735 14.5 to 16 magneti- should o cally be near a~2.862 A (1) (32) isotropic zero 15 (rod) (1) alloy (33) (31) 9 (waffle- (32) iron) (31) 7 Ni-Fe-Al ref.; (1), see section on thin p 386 for film papers the phase diagram.