scholarly journals Toroidal magnetic states in molecular wheels: Interplay between isotropic exchange interactions and local magnetic anisotropy

2008 ◽  
Vol 77 (22) ◽  
Author(s):  
Alessandro Soncini ◽  
Liviu F. Chibotaru
Keyword(s):  
Magnetic Anisotropy ◽  
Exchange Interactions ◽  
Isotropic Exchange ◽  
Magnetic States

scholarly journals Some new trends in the design of single molecule magnets

2017 ◽  
Vol 89 (8) ◽  
pp. 1119-1143 ◽  
Author(s):  
Sergey M. Aldoshin ◽  
Denis V. Korchagin ◽  
Andrew V. Palii ◽  
Boris S. Tsukerblat
Keyword(s):  
Magnetic Anisotropy ◽  
Metal Ions ◽  
Single Molecule ◽  
Exchange Interactions ◽  
Structural Factors ◽  
Single Molecule Magnets ◽  
Crystal Fields ◽  
Angular Momenta ◽  
Isotropic Exchange

AbstractIn this review we briefly discuss some new trends in the design of single molecule magnets based on transition (3d, 4d, 5d) and rare-earth (4f) metal ions. Within this broad theme the emphasis of the present review is placed on the molecules which exhibit strong magnetic anisotropy originating from the unquenched orbital angular momenta in the ground orbitally degenerate (or quasi-degenerate) states. Along with the general concepts we consider selected examples of the systems comprising orbitally-degenerate metal ions and demonstrate how one can benefit from strong single-ion anisotropy arising from the first-order orbital angular momentum. The role of crystal fields, spin-orbit coupling and structural factors is discussed. Some observation stemming from the analysis of the isotropic exchange interactions, magnetic anisotropy and strongly anisotropic orbitally-dependent superexchange are summarized as guiding rules for the controlled design of single molecule magnets exhibiting high barriers for magnetization reversal and, consequently, high blocking temperatures.

scholarly journals Isotropic Nature of the Metallic Kagome Ferromagnet Fe3Sn2 at High Temperatures

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 307
Author(s):  
Rebecca L. Dally ◽  
Daniel Phelan ◽  
Nicholas Bishop ◽  
Nirmal J. Ghimire ◽  
Jeffrey W. Lynn
Keyword(s):  
Elevated Temperatures ◽  
Magnetocrystalline Anisotropy ◽  
Inelastic Neutron Scattering ◽  
Exchange Interactions ◽  
Inelastic Neutron ◽  
Temperature Threshold ◽  
Magnetic Exchange ◽  
Spatial Anisotropy ◽  
Isotropic Exchange ◽  
State Spin

Anisotropy and competing exchange interactions have emerged as two central ingredients needed for centrosymmetric materials to exhibit topological spin textures. Fe3Sn2 is thought to have these ingredients as well, as it has recently been discovered to host room temperature skyrmionic bubbles with an accompanying topological Hall effect. We present small-angle inelastic neutron scattering measurements that unambiguously show that Fe3Sn2 is an isotropic ferromagnet below TC≈660 K to at least 480 K—the lower temperature threshold of our experimental configuration. Fe3Sn2 is known to have competing magnetic exchange interactions, correlated electron behavior, weak magnetocrystalline anisotropy, and lattice (spatial) anisotropy; all of these features are thought to play a role in stabilizing skyrmions in centrosymmetric systems. Our results reveal that at the elevated temperatures measured, there is an absence of significant magnetocrystalline anisotropy and that the system behaves as a nearly ideal isotropic exchange interaction ferromagnet, with a spin stiffness D(T=480 K)=168 meV Å2, which extrapolates to a ground state spin stiffness D(T=0 K)=231 meV Å2.

Competing exchange interactions and magnetic anisotropy of La1−Tb Mn2Si2

2017 ◽  
Vol 422 ◽  
pp. 237-242 ◽  
Author(s):  
E.G. Gerasimov ◽  
N.V. Mushnikov ◽  
P.B. Terentev ◽  
K.A. Yazovskikh ◽  
I.S. Titov ◽  
...  
Keyword(s):  
Magnetic Anisotropy ◽  
Exchange Interactions

MAGNETIC ELEMENTS OF NEURAL NETWORKS. PROPERTIES OF MAGNETIC INHOMOGENEITIES IN RESTRICTED GEOMETRIES

2021 ◽  
Vol 0 (1) ◽  
pp. 81-86
Author(s):  
A.R. MINIBAEVA ◽  
◽  
Z.V. GAREEVA ◽  
Keyword(s):  
Neural Network ◽  
Neural Networks ◽  
Magnetic Anisotropy ◽  
Domain Structure ◽  
Magnetic State ◽  
Magnetic Nanostructures ◽  
External Factors ◽  
Magnetic Elements ◽  
Magnetic States ◽  
Moriya Interaction

This paper discusses the prospects for using magnetic nanostructures as elements of neural networks. At present neural network learning programs are actively used in analyzing and processing large data arrays; however, the development of computer technologies based on the neural network principle still remains open. Possibilities for using magnetic elements as physical carriers of information bits in these systems attract much attention from researchers and technologists due to the presence of several easily controlled parameters (order parameter) in the magnetic system, possibilities for the dimensionality reduction in magnetic elements by using magnetic nanostructures (domain boundaries, vortices, ckyrmions), superquick switching between magnetic states and some other factors. One of the key aspects of research in this regard is to determine basic controlled magnetic parameters in restricted geometries and to identify ways of controlling these parameters through internal and external factors. The paper presents a research on the magnetic ground state in restricted geometries. It deals with the magnetic state rebuilding in the system under changes in both external factors (applied magnetic field, sample dimensions) and internal ones (magnetic anisotropy constant, Dzyaloshinskii-Moriya interaction constant). Calculations were performed within the framework of micromagnetic modelling using the Object Oriented MicroMagnetic Framework ( OOMMF) sogtware. It is shown that the anisotropic exchange interaction (Dzyaloshinskii-Moriya interaction) has a significant effect on the magnetization distribution in restricted geometries. Namely, when changing the value of the Dzyaloshinskii-Moriya constant in the system with uniaxial magnetic anisotropy there is a series of phase transitions observed between magnetic states of different types: transitions from the homogenous magnetic state into the skyrmion-type vortex state (domain structure with the skyrmion-type unidomain state) with subsequent domain structure reversal when changing the value of the Dzyaloshinskii-Moriya constant. In the case of magnetic anisotropy of easy -axis type, chirality and properties of the structures in question do not depend on the constant symbol of the Dzyaloshinskii-Moriya interaction.

Magnetic anisotropy and exchange interactions in Li-Al ferrites

1982 ◽  
Vol 25 (11) ◽  
pp. 1022-1025
Author(s):  
N. L. Pakhomova ◽  
V. A. Kozlov
Keyword(s):  
Magnetic Anisotropy ◽  
Exchange Interactions

Effect of Biquadratic Exchange Upon Ferromagnetic Two-Magnon Bound States. II. Anisotropic Exchange

1974 ◽  
Vol 52 (1) ◽  
pp. 33-39 ◽  
Author(s):  
D. A. Pink ◽  
R. Ballard
Keyword(s):  
Bound States ◽  
Exchange Interactions ◽  
Bound State ◽  
Exchange Term ◽  
Zero Temperature ◽  
Biquadratic Exchange ◽  
Anisotropic Exchange ◽  
Bound State Spectrum ◽  
Mode Pair ◽  
Isotropic Exchange

We have investigated the two-magnon bound state spectrum of a ferromagnetically ordered system for which the Hamiltonian contains an anisotropic bilinear exchange term, an anisotropic biquadratic exchange term, and a single-ion anisotropy term. The bound states, labelled by a wave vector q which we have taken to be in the [111] direction, were calculated by using zero-temperature Green functions. The principal results are: (i) the existence of single-ion bound states in the absence of single-ion anisotropy and conversely, their absence in the presence of such anisotropy, in contrast to the case in which the exchange interactions are isotropic; (ii) the appearance of an S mode for values of q, [Formula: see text]; (iii) the ordering of bound states for isotropic exchange interactions wherein the S0 mode lies below the S1-mode, D-mode pair and where the S1 mode lies below (above) the D mode if they lie below (above) the band, no longer holds.

scholarly journals Low-field Magnetic Anisotropy of Sr2IrO4

2022 ◽  
Author(s):  
Muhammad Nauman ◽  
Tayyaba Hussain ◽  
Joonyoung Choi ◽  
Nara Lee ◽  
Young Jai Choi ◽  
...  
Keyword(s):  
Magnetic Anisotropy ◽  
Exchange Interaction ◽  
Exchange Interactions ◽  
Orbit Coupling ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Easy Magnetization ◽  
Magnetic Exchange ◽  
Crystal Field Effect ◽  
Out Of Plane

Abstract Magnetic anisotropy in strontium iridate (Sr2IrO4) is essential because of its strong spin–orbit coupling and crystal field effect. In this paper, we present a detailed mapping of the out-of-plane (OOP) magnetic anisotropy in Sr2IrO4 for different sample orientations using torque magnetometry measurements in the low-magnetic-field region before the isospins are completely ordered. Dominant in-plane anisotropy was identified at low fields, confirming the b axis as an easy magnetization axis. Based on the fitting analysis of the strong uniaxial magnetic anisotropy, we observed that the main anisotropic effect arises from a spin–orbit-coupled magnetic exchange interaction affecting the OOP interaction. The effect of interlayer exchange interaction results in additional anisotropic terms owing to the tilting of the isospins. The results are relevant for understanding OOP magnetic anisotropy and provide a new way to analyze the effects of spin–orbit-coupling and interlayer magnetic exchange interactions. This study provides insight into the understanding of bulk magnetic, magnetotransport, and spintronic behavior on Sr2IrO4 for future studies.

Exchange interactions in antiferromagnetic salts of iridium II. Magnetic susceptibility measurements

1959 ◽  
Vol 250 (1260) ◽  
pp. 97-109 ◽  
Keyword(s):  
Magnetic Susceptibility ◽  
Exchange Interaction ◽  
Ammonium Salt ◽  
Potassium Salt ◽  
Room Temperature ◽  
Exchange Interactions ◽  
Nearest Neighbour ◽  
Paramagnetic Resonance ◽  
Magnetic Susceptibilities ◽  
Isotropic Exchange

Measurements have been made of the magnetic susceptibilities of ammonium and potassium chloroiridates at temperatures between room temperature and 1°K. The results obtained at high temperatures have been analysed into a susceptibility following a Curie-Weiss law together with temperature-independent terms. The values of the isotropic exchange inter­actions between neighbouring iridium ions deduced from the Weiss constant agree well with those calculated from paramagnetic resonance measurements. At lower temperatures the magnetic susceptibilities become almost independent of temperature over a certain range and then fall sharply at the antiferromagnetic transtion points (2.16 °K for the ammonium salt, 3.08°K for the potassium salt). These results are discussed in term s of the exchange interaction between nearest- and next-nearest-neighbour iridium ions.

scholarly journals Exchange interactions and magnetic anisotropy in the ‘Ni4’ magnetic molecule

2005 ◽  
Vol 78 (1-3) ◽  
pp. 47-59 ◽  
Author(s):  
A.V. Postnikov ◽  
M. Brüger ◽  
J. Schnack
Keyword(s):  
Magnetic Anisotropy ◽  
Exchange Interactions
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