scholarly journals Designing magnetic superlattices that are composed of single domain nanomagnets

2014 ◽  
Vol 5 ◽  
pp. 956-963 ◽  
Author(s):  
Derek M Forrester ◽  
Feodor V Kusmartsev ◽  
Endre Kovács
Keyword(s):  
Phase Diagrams ◽  
Coupling Strength ◽  
Magnetic Moments ◽  
Magnetic Hysteresis ◽  
Single Domain ◽  
Magnetic Interactions ◽  
Dynamical Analysis ◽  
Complex Nature ◽  
Phase Boundaries ◽  
Average Magnetization

Background: The complex nature of the magnetic interactions between any number of nanosized elements of a magnetic superlattice can be described by the generic behavior that is presented here. The hysteresis characteristics of interacting elliptical nanomagnets are described by a quasi-static method that identifies the critical boundaries between magnetic phases. A full dynamical analysis is conducted in complement to this and the deviations from the quasi-static analysis are highlighted. Each phase is defined by the configuration of the magnetic moments of the chain of single domain nanomagnets and correspondingly the existence of parallel, anti-parallel and canting average magnetization states. Results: We give examples of the phase diagrams in terms of anisotropy and coupling strength for two, three and four magnetic layers. Each phase diagrams character is defined by the shape of the magnetic hysteresis profile for a system in an applied magnetic field. We present the analytical solutions that enable one to define the “phase” boundaries between the emergence of spin-flop, anti-parallel and parallel configurations. The shape of the hysteresis profile is a function of the coupling strength between the nanomagnets and examples are given of how it dictates a systems magnetic response. Many different paths between metastable states can exist and this can lead to instabilities and fluctuations in the magnetization. Conclusion: With these phase diagrams one can find the most stable magnetic configurations against perturbations so as to create magnetic devices. On the other hand, one may require a magnetic system that can easily be switched between phases, and so one can use the information herein to design superlattices of the required shape and character by choosing parameters close to the phase boundaries. This work will be useful when designing future spintronic devices, especially those manipulating the properties of CoFeB compounds.

Investigation on the Origin of Magnetization in Plastically Deformed NI51TI49 Alloy

2017 ◽  
Vol 743 ◽  
pp. 13-18
Author(s):  
Anna Drozdova ◽  
Alexander Nyavro ◽  
Lyudmila Kveglis
Keyword(s):  
Crystal Lattice ◽  
Magnetic Moments ◽  
Magnetic Hysteresis ◽  
Hysteresis Loops ◽  
Lattice Curvature ◽  
Electron States ◽  
Large Atom ◽  
Transmission Electron ◽  
Large Distortion ◽  
Density Of Electron States

The article deals with the investigation of structure and magnetic properties of plastically deformed Ni51Ti49 alloy. The magnetic hysteresis loops confirm the presence of ferromagnetic properties in the alloy. The transmission electron microscopy (TEM) detects the appearance of lenticular crystals with bending contours which indicate the large distortion of the crystal lattice. The crystal lattice curvature occurs due to the large atom displacement. As a result, icosahedral clusters with the Frank-Kasper (FK) structure can be formed. The spin-polarized density of electron states and the magnetic moments for both non-deformed (near-spherical structure) and deformed (elongated by 5% along the Z-axis) Ni7Ti5 (FK-12), Ni8Ti5 (FK-13), and Ni10Ti6 (FK-16) clusters are calculated for the explanation of possibility of magnetization appearance in Ni51Ti49 alloy. The calculations show the increase in the magnetic moments for the deformed clusters. The calculated spectra demonstrate the high density of electron states near the Fermi level which is a characteristic feature of ferromagnetic alloys.

Phase diagrams for impurity-doped VO2

1976 ◽  
Vol 54 (1) ◽  
pp. 1-8 ◽  
Author(s):  
J. M. Reyes ◽  
S. L. Segel ◽  
M. Sayer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Phase Diagrams ◽  
Phase Region ◽  
Mixed Phase ◽  
Phase Boundaries ◽  
Temperature Changes ◽  
Impurity Doped ◽  
T Phase ◽  
Mixed Phase Region

The general form of the phase diagrams for impurity-doped VO2 is considered and shown to include mixed phase boundary regions. Phase diagrams for Cr and Al-doped VO2 are established on the basis of the temperature dependence of the 51V nuclear magnetic resonance (NMR) signal. In Cr-doped VO2, the (M2) phase is shown to exist over a smaller temperature–concentration range than reported previously and in Al-doped VO2, two intermediate single phases (M2) and (M3) are found. The (T) phase which has been previously suggested to be a definite phase having triclinic symmetry is shown to be a mixed phase region in which the contributions from the components change with temperature. Changes in NMR signal intensity at the phase boundaries show that half the V sites have paired spins in both the(M2) and (M3) phases.

scholarly journals Electric polarization from spiral order below 200K in multiferroic YBaCuFeO5

2014 ◽  
Vol 70 (a1) ◽  
pp. C388-C388
Author(s):  
Mickael Morin ◽  
Denis Scheptyakov ◽  
Lukas Keller ◽  
Juan Rodríguez-Carvajal ◽  
Andrea Scaramucci ◽  
...  
Keyword(s):  
Magnetic Order ◽  
Magnetic Moments ◽  
Double Perovskite ◽  
Electric Polarization ◽  
Ferroelectric Materials ◽  
Point Of View ◽  
Spin Reorientation ◽  
Magnetic Interactions ◽  
Practical Applications ◽  
Spiral Model

Ferroelectric materials have been known for almost one century [1]. While their potential for applications was rapidly recognized, the possibility of combining ferroelectricity with magnetic order -preferably with ferromagnetism- has resulted in an enormous deal of interest during the last decade. Several new materials combining both types of order have been recently reported, although their promising multifunctionalities have been obscured by two facts: on one side, most of them are antiferromagnetic; on the other, their transition temperatures, typically below 40K, are too low for most practical applications. The oxygen-defficient double perovskite YBaFeCuO5 constitutes a remarkable exception. Spontaneous electric polarization has been recently reported to exist below an unusually high temperature of TC ≍ 200K [2] coinciding with the occurrence of a commensurate - to - incommensurate reorientation of the Fe3+ and Cu2+ magnetic moments [3,4]. From a more fundamental point of view the observation of incommensurable magnetic order in a tetragonal material at such high temperatures is rather surprising. In particular, the nature of the relevant competing magnetic interactions and its possible link to low dimensionality or geometrical frustration is not understood at present. Although the existence of the spin reorientation in this material is known since 1995 [3] the low temperature magnetic structure has not yet been solved. Using neutron powder diffraction we have recently been able to propose a spiral model which satisfactorily describes the measured magnetic intensities below TC. Further, investigation of the crystal structure showed the existence of small anomalies in the lattice parameters and some interatomic distances at TC. The relevance of these findings for the magnetoelectric coupling, the direction of the polarization, the modification of the different exchange paths in the structure and the stabilization of the incommensurate magnetic order below TC is discussed.

Magnetic Condition Flat Core/Shell Nanoparticles

2015 ◽  
Vol 752-753 ◽  
pp. 238-242 ◽  
Author(s):  
Leonid Afremov ◽  
Artur Elovskii
Keyword(s):  
Phase Diagrams ◽  
Equilibrium Position ◽  
Magnetic Moments ◽  
Core Shell ◽  
Geometrical Parameters ◽  
Shell Nanoparticles ◽  
Two Phase ◽  
Magnetic Condition ◽  
Core Shell Nanoparticles ◽  
Magnetic States

In terms two-phase nanoparticles model, dependence equilibrium position of magnetic moments of parameters size and elongation nanoparticles core is investigated. Phase diagrams of magnetic states were shown and determine geometrical parameters core, in equilibrium states.

Average magnetization and local magnetic moments ofFeNclusters(N<230)

1999 ◽  
Vol 60 (1) ◽  
pp. 434-439 ◽  
Author(s):  
J. A. Franco ◽  
A. Vega ◽  
F. Aguilera-Granja
Keyword(s):  
Magnetic Moments ◽  
Average Magnetization

Nuclear acoustic resonance in europium vanadate

1995 ◽  
Vol 450 (1940) ◽  
pp. 719-722
Keyword(s):  
Acoustic Waves ◽  
Magnetic Moments ◽  
Preceding Paper ◽  
Electric Quadrupole ◽  
Acoustic Resonance ◽  
Magnetic Interactions ◽  
Nuclear Spins ◽  
Europium Ion ◽  
Nuclear Magnetic Moments ◽  
Hyperfine Splittings

The trivalent europium ion has a ground manifold 4f 6 , 7 F, in which the lowest state is J = 0, some 360 cm -1 below the first excited state J = 1. The two stable isotopes of mass 151, 153 each have nuclear spins I = 5/2. Experiments to determine the hyperfine structure are discussed in the preceding paper I; a further alternative is the use of acoustic waves. These have no direct interactions with the nuclear magnetic moments, but absorption arises through modulation of the electronic contributions to the hyperfine splittings. Nuclear electric quadrupole interactions are larger than magnetic interactions, and modulation of the electric field gradient of the lattice is expected to give a stronger effect.

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