DOCSLIB.ORG

Design, Synthesis and Magnetism of Single-Molecule Magnets with Large Anisotropic Barriers

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Design, Synthesis and Magnetism of Single-Molecule Magnets with Large Anisotropic Barriers Design, Synthesis and Magnetism of Single-Molecule Magnets with Large Anisotropic Barriers Po-Heng Lin PhD. thesis submitted to the Faculty of Graduate and Postdoctoral Studies In partial fulfillment of the requirements For the PhD. Degree in the Faculty of Science, Department of Chemistry Supervisor: Dr. Muralee Murugesu Department of Chemistry Faculty of Science University of Ottawa © Po-Heng Lin, Ottawa, Canada, 2012 Page | i Abstract This thesis will present the synthesis, characterization and magnetic measurements of III III III lanthanide complexes with varying nuclearities (Ln, Ln2, Ln3 and Ln4). Eu , Gd , Tb , DyIII, HoIII and YbIII have been selected as the metal centers. Eight polydentate Schiff-base ligands have been synthesized with N- and mostly O-based coordination environments which chelate 7-, 8- or 9-coordinate lanthanide ions. The molecular structures were characterized by single crystal X-ray crystallography and the magnetic properties were measured using a SQUID magnetometer. Each chapter consists of crystal structures and magnetic measurements for complexes with the same nuclearity. There are eight DyIII SMMs in this thesis which are discrete molecules that act as magnets below a certain temperature called their blocking temperature. This phenomenon results from an appreciable spin ground state (S) as well as negative uni-axial anisotropy (D), both present in lanthanide ions owing to their f electron shell, generating an effective energy barrier for the reversal of the magnetization (Ueff). The ab initio calculations are also included for the SMMs with high anisotropic energy barriers to understand the mechanisms of slow magnetic relaxation in these systems. Page | ii Acknowledgements and Contributions There are many people who deserve a special mention for their invaluable help with this research project: First and foremost my supervisor Prof. Muralee Murugesu who taught me inorganic chemistry and molecular magnetism. Thanks for all your patience over the years and spent a lot of time on correcting my English. Thanks for the skating and snowboarding lessons, whiskey tastings, rum tastings and philosophy education. I would like to say if you did not push me so hard in these five years, I would not have this many results and publications. Wan-Jou Hsu for waiting for me in Taiwan for five years. You are my best support when I feel frustrated. Thanks for giving up your high salary job, marrying me and staying with me in my PhD. last year. Love you forever. Fatemah Habib for all the help with anything and everything not only in chemistry. Thanks for all your patience for correcting my writing and listening to my practices again and again. Thanks for letting me know that “women’s rights” are so important. Dr. Jérôme Long for all his help with theoretical aspects of molecular magnetism and teaching me how to use the SQUID. Moreover, I will never forget the awesome conference memories, especially the wheelchair. Dr. Ilia Korobkov and Dr. Tara J. Burchell for all the crystal structures presented in this thesis and for always finding that one crystal that worked. Dr. Cyril Cook for all his help with organic chemistry. Prof. Rodolphe Clérac for SQUID measurements and Dr. Wolfgang Wernsdorfer for micro-SQUID measurements. Prof. Liviu Chibtaru and Dr. Liviu Ungur in Belgium for all the ab initio calculations. Jennifer Le Roy for “some” beers and wonderful Canadian experience. Last but certainly not least, thanks to all the lab members, past and present, for making time in the lab enjoyable and fun. Page | iii Table of Contents Chapter 1: Introduction ................................................................................... 1 1.1 Magnetic properties of material .................................................................................... 2 1.1.1 Diamagnetism .............................................................................................. 2 1.1.2 Paramagnetism ............................................................................................. 3 1.1.3 Ferromagnetism ........................................................................................... 4 1.1.4 Anti-ferromagnetism .................................................................................... 5 1.1.5 Ferrimagnetism ............................................................................................ 5 1.2 Basic principle of magnetic properties .......................................................................... 6 1.2.1 Fundamental Physical Constants ............................................................... 6 1.2.2 Curie Law and Curie-Weiss Law .............................................................. 7 1.2.3 Van Vleck equation ................................................................................... 8 1.2.4 Derivation of magnetic susceptibility ...................................................... 10 1.2.5 Magnetic anisotropy ................................................................................ 13 1.2.6 Magnetometer .......................................................................................... 15 1.3 Single-Molecule Magnets (SMMs) ............................................................................. 17 1.4 Magnetic measurements for SMMs .......................................................................... 22 1.5 Lanthanide chemistry .................................................................................................. 30 1.6 Magnetic properties of LnIII ions ................................................................................. 32 1.7 Lanthanide SMMs ....................................................................................................... 35 1.8 Ligand design .............................................................................................................. 40 1.9 Thesis overview........................................................................................................... 47 Page | iv Chapter 2: Mononuclear lanthanide complexes ............................................ 48 2.1 Molecular structure of [Tb(Hhmi)(NO3)2(MeOH)2] (2-1) .......................................... 49 2.2 Molecular structure of [Ln(H2hmi)(DMF)2Cl2]Cl·2(CH3CN) (Ln: Tb(2-2) and Yb(2-3)) .. .............................................................................................................. 51 2.3 Molecular structure of [Dy(Hhmb)(DMF)2Cl2] (2-4·) .............................................. 53 2.4 Molecular structure of [Ln(Hhmb)(bp)(NO3)2]·MeCN (Ln: Tb(2-5), Dy(2-6) and Ho(2-7)) ................................................................................................................. 55 2.5 Molecular structure of [Dy(Hhma)(DMF)2Cl2] (2-8) ................................................. 58 2.6 Molecular structure of [Dy(hmf)(DETA)2]Cl·2CH2Cl2·MeOH (2-9) ......................... 61 2.7 Molecular structure and magnetism of [Dy(H2hmt)(NO3)4(DMF)2] (2-10) ............... 64 Chapter 3: Dinuclear complexes ................................................................... 77 3.1 Molecular structure and magnetism of [Dy2(Hhmb)2(NO3)4]·MeCN (3-1) ................ 78 3.2 Molecular structure and magnetism of [Dy2(Hhmb)2(NO3)4(N3)2(MeOH)]·2MeOH (3-2) ....................................................................................................................... 84 3.3 Molecular structure and magnetism of Dy2(Hhma)3(NO3)3·CH3CN·2MeOH (3-3) ... 93 3.4 Molecular structure of [Ln2(hmi)2(NO3)x(MeOH)y] (Ln: Eu, Gd, Tb and Dy, x = 2 and y = 2 or 4) ............................................................................................................ 99 3.5 Magnetic measurement of complexes 3-4 – 3-11 ..................................................... 119 3.5.1 DC measurement ..................................................................................... 119 3.5.2 AC measurement ..................................................................................... 127 Chapter 4: Trinuclear complexes ................................................................ 143 4.1 Molecular structure and magnetism of 3N(CH3)4·[Ln3(hmf)6]·2CH3OH·H2O (Ln: Dy(4-1), Tb(4-2)) ................................................................................................ 144 Page | v 4.2 Molecular structure and magnetism of 3N(CH3)4·[Dy3(hef)6]·2CH3OH·H2O (4-3) . 154 4.3 Structure and magnetism of [Dy3(3-OMe)(hbb)3(NO3)(CH3OH)2]·3(NO3)·5(CH3OH) (4-4) ..................................................................................................................... 164 4.4 Structure and magnetism of [Dy3(3-OH)2(-OMe)(hmi)2(MeOH)4(H2O)2]·Cl2 (4-5) ............................................................................................................................. 177 Chapter 5: Tetranuclear complexes ............................................................. 190 5.1 Molecular structure and magnetism of [Ln4(µ3-OH)2(bmh)2(msh)4Cl2] (Ln: Dy(5-1), Tb(5-2) and Ho(5-3)) ........................................................................................... 191 5.2 Molecular structure and magnetism of [Dy4(µ4-O)(µ-OMe)2(beh)2(esh)4]·3MeOH (5-4) ..................................................................................................................... 213 Chapter 6: Conclusion ................................................................................. 232 Chapter 7: Experimental ............................................................................. 243 Chapter
Load more

Recommended publications
  • Canted Ferrimagnetism and Giant Coercivity in the Non-Stoichiometric
    Canted ferrimagnetism and giant coercivity in the non-stoichiometric double perovskite La2Ni1.19Os0.81O6 Hai L. Feng1, Manfred Reehuis2, Peter Adler1, Zhiwei Hu1, Michael Nicklas1, Andreas Hoser2, Shih-Chang Weng3, Claudia Felser1, Martin Jansen1 1Max Planck Institute for Chemical Physics of Solids, Dresden, D-01187, Germany 2Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, D-14109, Germany 3National Synchrotron Radiation Research Center (NSRRC), Hsinchu, 30076, Taiwan Abstract: The non-stoichiometric double perovskite oxide La2Ni1.19Os0.81O6 was synthesized by solid state reaction and its crystal and magnetic structures were investigated by powder x-ray and neutron diffraction. La2Ni1.19Os0.81O6 crystallizes in the monoclinic double perovskite structure (general formula A2BB’O6) with space group P21/n, where the B site is fully occupied by Ni and the B’ site by 19 % Ni and 81 % Os atoms. Using x-ray absorption spectroscopy an Os4.5+ oxidation state was established, suggesting presence of about 50 % 5+ 3 4+ 4 paramagnetic Os (5d , S = 3/2) and 50 % non-magnetic Os (5d , Jeff = 0) ions at the B’ sites. Magnetization and neutron diffraction measurements on La2Ni1.19Os0.81O6 provide evidence for a ferrimagnetic transition at 125 K. The analysis of the neutron data suggests a canted ferrimagnetic spin structure with collinear Ni2+ spin chains extending along the c axis but a non-collinear spin alignment within the ab plane. The magnetization curve of La2Ni1.19Os0.81O6 features a hysteresis with a very high coercive field, HC = 41 kOe, at T = 5 K, which is explained in terms of large magnetocrystalline anisotropy due to the presence of Os ions together with atomic disorder.
    [Show full text]
  • Magnetism, Magnetic Properties, Magnetochemistry
    Magnetism, Magnetic Properties, Magnetochemistry 1 Magnetism All matter is electronic Positive/negative charges - bound by Coulombic forces Result of electric field E between charges, electric dipole Electric and magnetic fields = the electromagnetic interaction (Oersted, Maxwell) Electric field = electric +/ charges, electric dipole Magnetic field ??No source?? No magnetic charges, N-S No magnetic monopole Magnetic field = motion of electric charges (electric current, atomic motions) Magnetic dipole – magnetic moment = i A [A m2] 2 Electromagnetic Fields 3 Magnetism Magnetic field = motion of electric charges • Macro - electric current • Micro - spin + orbital momentum Ampère 1822 Poisson model Magnetic dipole – magnetic (dipole) moment [A m2] i A 4 Ampere model Magnetism Microscopic explanation of source of magnetism = Fundamental quantum magnets Unpaired electrons = spins (Bohr 1913) Atomic building blocks (protons, neutrons and electrons = fermions) possess an intrinsic magnetic moment Relativistic quantum theory (P. Dirac 1928) SPIN (quantum property ~ rotation of charged particles) Spin (½ for all fermions) gives rise to a magnetic moment 5 Atomic Motions of Electric Charges The origins for the magnetic moment of a free atom Motions of Electric Charges: 1) The spins of the electrons S. Unpaired spins give a paramagnetic contribution. Paired spins give a diamagnetic contribution. 2) The orbital angular momentum L of the electrons about the nucleus, degenerate orbitals, paramagnetic contribution. The change in the orbital moment
    [Show full text]
  • Chapter 6 Antiferromagnetism and Other Magnetic Ordeer
    Chapter 6 Antiferromagnetism and Other Magnetic Ordeer 6.1 Mean Field Theory of Antiferromagnetism 6.2 Ferrimagnets 6.3 Frustration 6.4 Amorphous Magnets 6.5 Spin Glasses 6.6 Magnetic Model Compounds TCD February 2007 1 1 Molecular Field Theory of Antiferromagnetism 2 equal and oppositely-directed magnetic sublattices 2 Weiss coefficients to represent inter- and intra-sublattice interactions. HAi = n’WMA + nWMB +H HBi = nWMA + n’WMB +H Magnetization of each sublattice is represented by a Brillouin function, and each falls to zero at the critical temperature TN (Néel temperature) Sublattice magnetisation Sublattice magnetisation for antiferromagnet TCD February 2007 2 Above TN The condition for the appearance of spontaneous sublattice magnetization is that these equations have a nonzero solution in zero applied field Curie Weiss ! C = 2C’, P = C’(n’W + nW) TCD February 2007 3 The antiferromagnetic axis along which the sublattice magnetizations lie is determined by magnetocrystalline anisotropy Response below TN depends on the direction of H relative to this axis. No shape anisotropy (no demagnetizing field) TCD February 2007 4 Spin Flop Occurs at Hsf when energies of paralell and perpendicular configurations are equal: HK is the effective anisotropy field i 1/2 This reduces to Hsf = 2(HKH ) for T << TN Spin Waves General: " n h q ~ q ! M and specific heat ~ Tq/n Antiferromagnet: " h q ~ q ! M and specific heat ~ Tq TCD February 2007 5 2 Ferrimagnetism Antiferromagnet with 2 unequal sublattices ! YIG (Y3Fe5O12) Iron occupies 2 crystallographic sites one octahedral (16a) & one tetrahedral (24d) with O ! Magnetite(Fe3O4) Iron again occupies 2 crystallographic sites one tetrahedral (8a – A site) & one octahedral (16d – B site) 3 Weiss Coefficients to account for inter- and intra-sublattice interaction TCD February 2007 6 Below TN, magnetisation of each sublattice is zero.
    [Show full text]
  • Multidisciplinary Design Project Engineering Dictionary Version 0.0.2
    Multidisciplinary Design Project Engineering Dictionary Version 0.0.2 February 15, 2006 . DRAFT Cambridge-MIT Institute Multidisciplinary Design Project This Dictionary/Glossary of Engineering terms has been compiled to compliment the work developed as part of the Multi-disciplinary Design Project (MDP), which is a programme to develop teaching material and kits to aid the running of mechtronics projects in Universities and Schools. The project is being carried out with support from the Cambridge-MIT Institute undergraduate teaching programe. For more information about the project please visit the MDP website at http://www-mdp.eng.cam.ac.uk or contact Dr. Peter Long Prof. Alex Slocum Cambridge University Engineering Department Massachusetts Institute of Technology Trumpington Street, 77 Massachusetts Ave. Cambridge. Cambridge MA 02139-4307 CB2 1PZ. USA e-mail: [email protected] e-mail: [email protected] tel: +44 (0) 1223 332779 tel: +1 617 253 0012 For information about the CMI initiative please see Cambridge-MIT Institute website :- http://www.cambridge-mit.org CMI CMI, University of Cambridge Massachusetts Institute of Technology 10 Miller’s Yard, 77 Massachusetts Ave. Mill Lane, Cambridge MA 02139-4307 Cambridge. CB2 1RQ. USA tel: +44 (0) 1223 327207 tel. +1 617 253 7732 fax: +44 (0) 1223 765891 fax. +1 617 258 8539 . DRAFT 2 CMI-MDP Programme 1 Introduction This dictionary/glossary has not been developed as a definative work but as a useful reference book for engi- neering students to search when looking for the meaning of a word/phrase. It has been compiled from a number of existing glossaries together with a number of local additions.
    [Show full text]
  • Magnetism in Transition Metal Complexes
    Magnetism for Chemists I. Introduction to Magnetism II. Survey of Magnetic Behavior III. Van Vleck’s Equation III. Applications A. Complexed ions and SOC B. Inter-Atomic Magnetic “Exchange” Interactions © 2012, K.S. Suslick Magnetism Intro 1. Magnetic properties depend on # of unpaired e- and how they interact with one another. 2. Magnetic susceptibility measures ease of alignment of electron spins in an external magnetic field . 3. Magnetic response of e- to an external magnetic field ~ 1000 times that of even the most magnetic nuclei. 4. Best definition of a magnet: a solid in which more electrons point in one direction than in any other direction © 2012, K.S. Suslick 1 Uses of Magnetic Susceptibility 1. Determine # of unpaired e- 2. Magnitude of Spin-Orbit Coupling. 3. Thermal populations of low lying excited states (e.g., spin-crossover complexes). 4. Intra- and Inter- Molecular magnetic exchange interactions. © 2012, K.S. Suslick Response to a Magnetic Field • For a given Hexternal, the magnetic field in the material is B B = Magnetic Induction (tesla) inside the material current I • Magnetic susceptibility, (dimensionless) B > 0 measures the vacuum = 0 material response < 0 relative to a vacuum. H © 2012, K.S. Suslick 2 Magnetic field definitions B – magnetic induction Two quantities H – magnetic intensity describing a magnetic field (Système Internationale, SI) In vacuum: B = µ0H -7 -2 µ0 = 4π · 10 N A - the permeability of free space (the permeability constant) B = H (cgs: centimeter, gram, second) © 2012, K.S. Suslick Magnetism: Definitions The magnetic field inside a substance differs from the free- space value of the applied field: → → → H = H0 + ∆H inside sample applied field shielding/deshielding due to induced internal field Usually, this equation is rewritten as (physicists use B for H): → → → B = H0 + 4 π M magnetic induction magnetization (mag.
    [Show full text]
  • Condensed Matter Option MAGNETISM Handout 1
    Condensed Matter Option MAGNETISM Handout 1 Hilary 2014 Radu Coldea http://www2.physics.ox.ac.uk/students/course-materials/c3-condensed-matter-major-option Syllabus The lecture course on Magnetism in Condensed Matter Physics will be given in 7 lectures broken up into three parts as follows: 1. Isolated Ions Magnetic properties become particularly simple if we are able to ignore the interactions between ions. In this case we are able to treat the ions as effectively \isolated" and can discuss diamagnetism and paramagnetism. For the latter phenomenon we revise the derivation of the Brillouin function outlined in the third-year course. Ions in a solid interact with the crystal field and this strongly affects their properties, which can be probed experimentally using magnetic resonance (in particular ESR and NMR). 2. Interactions Now we turn on the interactions! I will discuss what sort of magnetic interactions there might be, including dipolar interactions and the different types of exchange interaction. The interactions lead to various types of ordered magnetic structures which can be measured using neutron diffraction. I will then discuss the mean-field Weiss model of ferromagnetism, antiferromagnetism and ferrimagnetism and also consider the magnetism of metals. 3. Symmetry breaking The concept of broken symmetry is at the heart of condensed matter physics. These lectures aim to explain how the existence of the crystalline order in solids, ferromagnetism and ferroelectricity, are all the result of symmetry breaking. The consequences of breaking symmetry are that systems show some kind of rigidity (in the case of ferromagnetism this is permanent magnetism), low temperature elementary excitations (in the case of ferromagnetism these are spin waves, also known as magnons), and defects (in the case of ferromagnetism these are domain walls).
    [Show full text]
  • Magnetochemistry
    Magnetochemistry (12.7.06) H.J. Deiseroth, SS 2006 Magnetochemistry The magnetic moment of a single atom (µ) (µ is a vector !) μ µ μ = i F [Am2], circular current i, aerea F F -27 2 μB = eh/4πme = 0,9274 10 Am (h: Planck constant, me: electron mass) μB: „Bohr magneton“ (smallest quantity of a magnetic moment) → for one unpaired electron in an atom („spin only“): s μ = 1,73 μB Magnetochemistry → The magnetic moment of an atom has two components a spin component („spin moment“) and an orbital component („orbital moment“). →Frequently the orbital moment is supressed („spin-only- magnetism“, e.g. coordination compounds of 3d elements) Magnetisation M and susceptibility χ M = (∑ μ)/V ∑ μ: sum of all magnetic moments μ in a given volume V, dimension: [Am2/m3 = A/m] The actual magnetization of a given sample is composed of the „intrinsic“ magnetization (susceptibility χ) and an external field H: M = H χ (χ: suszeptibility) Magnetochemistry There are three types of susceptibilities: χV: dimensionless (volume susceptibility) 3 χg:[cm/g] (gramm susceptibility) 3 χm: [cm /mol] (molar susceptibility) !!!!! χm is used normally in chemistry !!!! Frequently: χ = f(H) → complications !! Magnetochemistry Diamagnetism - external field is weakened - atoms/ions/molecules with closed shells -4 -2 3 -10 < χm < -10 cm /mol (negative sign) Paramagnetism (van Vleck) - external field is strengthened - atoms/ions/molecules with open shells/unpaired electrons -4 -1 3 +10 < χm < 10 cm /mol → diamagnetism (core electrons) + paramagnetism (valence electrons) Magnetism
    [Show full text]
  • A THEORY of FERROMAGNETISM by Linus PAULING
    VOL. 39, 1953 PHYSICS: L. PA ULING 551 1 These PROCEEDINGS, 37, 311 (1951). 2R. G., p. 17. This refers to the author's Riemannian Geometry, Princeton University Press. 3Eisenhart, L. P., "Non-Riemannian Geometry," Amer. Math. Soc. Colloquium Publications, 5, p. 5. 4R. G., p. 21. 6 Einstein, A., The Meaning of Relativity, Foturth Edition, Princeton University Press, pp. 144, 146, 147. 6 R. G., p. 82. A THEORY OF FERROMAGNETISM BY LINUs PAULING GATES AND CRELLIN LABORATORIES OF CHEMISTRY,* CALIFORNIA INSTITUTE OF T,CHNOLOGY Communicated April 1, 1953 The properties of ferromagnetic substances are in reasonably good accord with the theory of Weiss.' In this theory it is postulated that the atomic magnets tend to be brought into parallel orientation not only by an applied magnetic field but also by an inner field which is propor- tional to the magnetization of the substance. The inner field is not due to magnetic interaction of the magnetic moments of the molecules, but to electrostatic interactions, which are related to the orientation of the magnetic moments of electrons through the Pauli principle. During the past twenty-five years many efforts have been made to develop a precise theory of the interactions that produce the inner field, and to account in this way for the observed magnetic properties of ferromagnetic substances, but these attempts have not been successful-no one has published a theory of the electronic structure of ferromagnetic substances that permits reason- ably good predictions to be made of the values of the saturation magnetic moment and the Curie temperature.
    [Show full text]
  • Competition Between Ferrimagnetism and Magnetic Frustration in Zinc Substituted Ybafe4o7
    Competition between Ferrimagnetism and Magnetic Frustration in Zinc Substituted YBaFe4O7 Tapati Sarkar*, V. Pralong, V. Caignaert and B. Raveau Laboratoire CRISMAT, UMR 6508 CNRS ENSICAEN, 6 bd Maréchal Juin, 14050 CAEN, France Abstract The substitution of zinc for iron in YBaFe4O7 has allowed the oxide series YBaFe4- xZnxO7, with 0.40 x 1.50, belonging to the “114” structural family to be synthesized. These oxides crystallize in the hexagonal symmetry (P63mc), as opposed to the cubic symmetry (F- 43m) of YBaFe4O7. Importantly, the d.c. magnetization shows that the zinc substitution induces ferrimagnetism, in contrast to the spin glass behaviour of YBaFe4O7. Moreover, a.c. susceptibility measurements demonstrate that concomitantly these oxides exhibit a spin glass or a cluster glass behaviour, which increases at the expense of ferrimagnetism, as the zinc content is increased. This competition between ferrimagnetism and magnetic frustration is interpreted in terms of lifting of the geometric frustration, inducing the magnetic ordering, and of cationic disordering, which favours the glassy state. * Corresponding author: Dr. Tapati Sarkar e-mail:[email protected] Fax: +33 2 31 95 16 00 Tel: +33 2 31 45 26 32 1 Introduction Transition metal oxides, involving a mixed valence of the transition element, present a great potential for the generation of strongly correlated electron systems. An extraordinary number of studies have been carried out in the last two decades on systems such as superconducting cuprates, colossal magnetoresistive manganites, and magnetic cobaltites, whose oxygen lattice exhibits a “square” symmetry derived from the perovskite structure. In contrast, the number of oxides with a triangular symmetry of the oxygen framework is much more limited, if one excludes the large family of spinels which exhibit exceptional ferrimagnetic properties and unique magnetic transitions [1 – 3] as for Fe3O4, but also magnetic frustration [4 – 5] due to the peculiar triangular geometry of their framework as for spinel ferrite thin films.
    [Show full text]
  • Antiferromagnetism and Ferrimagnetism a B Lidiard - Ferrites to Cite This Article: Louis Néel 1952 Proc
    Proceedings of the Physical Society. Section A Related content - Antiferromagnetism Antiferromagnetism and Ferrimagnetism A B Lidiard - Ferrites To cite this article: Louis Néel 1952 Proc. Phys. Soc. A 65 869 A Fairweather, F F Roberts and A J E Welch - Ferrimagnetism W P Wolf View the article online for updates and enhancements. Recent citations - Magnetic Structure and Metamagnetic Transitions in the van der Waals Antiferromagnet CrPS4 Yuxuan Peng et al - Synthesis of CoFe2O4 Nanoparticles: The Effect of Ionic Strength, Concentration, and Precursor Type on Morphology and Magnetic Properties Izabela Malinowska et al - Impact of dehydration and mechanical amorphization on the magnetic properties of Ni(ii)-MOF-74 Senada Muratovi et al This content was downloaded from IP address 132.166.183.104 on 16/06/2020 at 16:29 THE PROCEEDINGS OF THE PHYSICAL SOCIETY Section A c VOL. 65, PART11 1 November 1952 No. 395A Antiferromagnetism and Ferrimagnetism* BY LOUIS NeEL Laboratoire d’filectrostatique et de Physique du MBtal, Universitk de Grenoble 7th Holweck Lecture, delivered 27th May 1952; MS. recaved 27th May 1952 ABSTRACT. The present position of our knowledge of antiferromagnetism, mcluding ferrimagnetism, is reviewed, and some very interesting phenomena concerning the magnetic behaviour of certain ferrites and of pyrrhotite are described and explained. I-A N T I FER R 0 MAGNET I S M $1. THE NEGATIVE MOLECULAR FIELD AND ANTIPARALLEL SYSTEMS E know that in his celebrated theory of ferromagnetism (Weiss 1907) represented the interactions between the magnetic moments of neigh- Wbouring atoms by means of a molecular field H,=d .... 0 (1) proportional to the magnetization J, n being a constant.
    [Show full text]
  • Magnetic Properties of Spinel Type Ferrites Depending on the Co
    Structural phase stability and Magnetism in Co2FeO4 spinel oxide I. Panneer Muthuselvam and R.N. Bhowmik* Department of Physics, Pondicherry University, R. Venkataraman Nagar, Kalapet, Pondicherry-605014, India *E-mail address for corresponding author: [email protected] Abstract We report a correlation between structural phase stability and magnetic properties of Co2FeO4 spinel oxide. We employed mechanical alloying and subsequent annealing to obtain the desired samples. The particle size of the samples changes from 25 nm to 45 nm. The structural phase separation of samples, except sample annealed at 9000C, into Co rich and Fe rich spinel phase has been examined from XRD spectrum, SEM picture, along with EDAX spectrum, and magnetic measurements. The present study indicated the ferrimagnetic character of Co2FeO4, irrespective of structural phase stability. The observation of mixed ferrimagnetic phases, associated with two Curie temperatures at TC1 and TC2 (>TC1), respectively, provides the additional support of the splitting of single cubic spinel phase in Co2FeO4 spinel oxide. Key words: A. Spinel Ferrite; B. Mechanical alloyed nanomaterial; C. Structural phase stability; D. Ferrimagnetism. PACS: 61.66.Fn, 61.46.-w, 75.75.+a, 75.50.Kj I. INTRODUCTION Spinel ferrites are represented by the formula unit AB2O4. Most of the spinel ferrites form cubic spinel structure with oxygen anions in fcc positions and cations in the tetrahedral and octahedral coordinated interstitial lattice sites, forming the A and B sublattices [1]. Depending upon the nature (magnetic or non-magnetic) and distribution of cations among A and B sublattices, spinel ferrites can exhibit properties of different type magnets, like: ferrimagnet, antiferromagnet and paramagnet.
    [Show full text]
  • Magnetite (Fe3o4) Nanoparticles in Biomedical Application: from Synthesis to Surface Functionalisation
    magnetochemistry Review Magnetite (Fe3O4) Nanoparticles in Biomedical Application: From Synthesis to Surface Functionalisation Lokesh Srinath Ganapathe 1, Mohd Ambri Mohamed 1 , Rozan Mohamad Yunus 2 and Dilla Duryha Berhanuddin 1,* 1 Institut Kejuruteraan Mikro dan Nanoelektronik (IMEN), Universiti Kebangsaan Malaysia, Bangi 43600, Selangor Darul Ehsan, Malaysia; [email protected] (L.S.G.); [email protected] (M.A.M.) 2 Fuel Cell Institute, Level 4, Research Complex, Universiti Kebangsaan Malaysia, Bangi 43600, Selangor, Malaysia; [email protected] * Correspondence: [email protected]; Tel.: +60-38911-8544 Received: 28 October 2020; Accepted: 20 November 2020; Published: 3 December 2020 Abstract: Nanotechnology has gained much attention for its potential application in medical science. Iron oxide nanoparticles have demonstrated a promising effect in various biomedical applications. In particular, magnetite (Fe3O4) nanoparticles are widely applied due to their biocompatibility, high magnetic susceptibility, chemical stability, innocuousness, high saturation magnetisation, and inexpensiveness. Magnetite (Fe3O4) exhibits superparamagnetism as its size shrinks in the single-domain region to around 20 nm, which is an essential property for use in biomedical applications. In this review, the application of magnetite nanoparticles (MNPs) in the biomedical field based on different synthesis approaches and various surface functionalisation materials was discussed. Firstly, a brief introduction on the MNP properties, such as physical, thermal, magnetic, and optical properties, is provided. Considering that the surface chemistry of MNPs plays an important role in the practical implementation of in vitro and in vivo applications, this review then focuses on several predominant synthesis methods and variations in the synthesis parameters of MNPs. The encapsulation of MNPs with organic and inorganic materials is also discussed.
    [Show full text]