scholarly journals Damping of Magnetoelastic Waves

2020 ◽  
Vol 65 (10) ◽  
pp. 912
Author(s):  
V. G. Bar’yakhtar ◽  
A. G. Danilevich
Keyword(s):  
Significant Role ◽  
Easy Axis ◽  
Dissipative Function ◽  
Relaxation Processes ◽  
Magnetoelastic Interaction ◽  
Dissipative Processes ◽  
Dispersion Law ◽  
Magnetoacoustic Waves ◽  
Magnetoelastic Waves ◽  
General Method

A general method for constructing a model of the dissipative function describing the relaxation processes induced by the damping of coupled magnetoacoustic waves in magnetically ordered materials has been developed. The obtained model is based on the symmetry of the magnet and describes both exchange and relativistic interactions in the crystal. The model accounts for the contributions of both the magnetic and elastic subsystems to the dissipation, as well asthe relaxation associated with the magnetoelastic interaction. The dispersion law for coupled magnetoelastic waves is calculated in the case of a uniaxial ferromagnet of the “easy axis” type. It is shown that the contribution of the magnetoelastic interaction to dissipative processes can play a significant role in the case of magnetoacoustic resonance.

Magnetoelastic Waves in Ferromagnets in the Vicinity of Lattice Structural Phase Transitions

2018 ◽  
Vol 63 (9) ◽  
pp. 836 ◽  
Author(s):  
V. G. Bar’yakhtar ◽  
A. G. Danilevich
Keyword(s):  
Phase Transitions ◽  
Structural Phase ◽  
Martensitic Phase ◽  
Spin Reorientation ◽  
Dissipative Function ◽  
Relaxation Processes ◽  
Magnetoelastic Interaction ◽  
Degenerate Ground State ◽  
Martensitic Phase Transformations ◽  
Magnetoelastic Waves

The dispersion laws for coupled magnetoelastic waves in ferromagnets with uniaxial or cubic symmetry have been calculated. The features of obtained dispersion laws in the vicinity of spin-reorientation phase transitions are analyzed. The interaction between elastic and spin waves is shown to depend on the direction of the ferromagnet magnetic moment. The influence of the magnetoelastic interaction on the dispersion law of quasispin waves in the degenerate ground state of a uniaxial “easy plane” ferromagnet is studied. The results of calculations show that the magnetoelastic interaction eliminates the degeneration and leads to the appearance of a magnetoacoustic gap in the ferromagnet spectrum. The behavior of the spectra of coupled magnetoelastic waves in the vicinity of lattice phase transitions, namely, in the vicinity of martensitic phase transformations in materials with the shape memory effect, is analyzed. The obtained results are used to interpret experimental data obtained for the Ni–Mn–Ga alloy. The phenomenon of a drastic decrease of the elastic moduli for this alloy, when approaching the martensitic phase transition point is explained theoretically. It is shown that the inhomogeneous magnetostriction is the main factor affecting the elastic characteristics of the material concerned. A model dissipative function describing the relaxation processes associated with a damping of coupled magnetoelastic waves in ferromagnets with cubic or uniaxial symmetry is developed. It takes the symmetry of a ferromagnet into account and describes both the exchange and relativistic interactions in the crystal.

Overturning of nonlinear acoustic waves. Part 1 A general method

1993 ◽  
Vol 252 ◽  
pp. 585-599 ◽  
Author(s):  
P. W. Hammerton ◽  
D. G. Crighton
Keyword(s):  
Acoustic Waves ◽  
Wave Equations ◽  
Harmonic Wave ◽  
Nonlinear Wave Equations ◽  
Relaxation Processes ◽  
Dissipation Term ◽  
Nonlinear Acoustic ◽  
Thermoviscous Dissipation ◽  
Relaxing Gas ◽  
General Method

We consider model nonlinear wave equations of the form ut + uux = [Hscr ](x,t;u, ux,…) arising in gasdynamics and other fields, [Hscr ] incorporating various linear mechanisms of dissipation and dispersion. If [Hscr ] includes a thermoviscous dissipation term ∈uxx, then it is generally believed that u(x,t) will remain single-valued for all t > 0 and all single-valued u(x, 0), for any ∈ > 0. The question addressed here is whether, if thermoviscous dissipation is excluded from [Hscr ], u(x, t) remains single-valued for all t > 0, or whether certain dissipative-dispersive mechanisms (such as relaxation processes) are in themselves insufficient to prevent wave overturning. To answer this we propose a numerical scheme based on the use of intrinsic coordinates ψ = ψ(s, t) to describe the waveform at each time. In this paper, the method is described and validated by comparisons with the exact solutions for certain [Hscr ] ([Hscr ] = 0, [Hscr ] = -αu, [Hscr ] = ∈uxx). These comparisons show that the scheme is free of numerical viscosity effects which preclude the solution of the problem by finite-difference or spectral methods applied to the signal u(x, t), that it can reliably distinguish between finite-time overturning and merely the formation of steep gradients, and that it can accurately predict the time of overturning when it does occur. Having established the validity of the method, attention can then be turned to those cases where criteria for overturning have not as yet been determined by conventional methods. In Part 2, harmonic wave propagation through a relaxing gas is investigated.

Two field-induced slow magnetic relaxation processes in a mononuclear Co(ii) complex with a distorted octahedral geometry

2016 ◽  
Vol 45 (22) ◽  
pp. 9279-9284 ◽  
Author(s):  
Jing Li ◽  
Yuan Han ◽  
Fan Cao ◽  
Rong-Min Wei ◽  
Yi-Quan Zhang ◽  
...  
Keyword(s):  
Single Molecule ◽  
Magnetic Relaxation ◽  
Easy Axis ◽  
Octahedral Geometry ◽  
Distorted Octahedral Geometry ◽  
Relaxation Processes ◽  
Single Molecule Magnet ◽  
Distorted Octahedral ◽  
Slow Magnetic Relaxation

An easy-axis distorted octahedral mononuclear Co(ii) single-molecule magnet showing two filed-induced slow magnetic relaxation processes.

A General Method for Spectrometer Design in the Scoff Approximation

1976 ◽  
Vol 34 ◽  
pp. 538-539
Author(s):  
J. R. Fields
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Energy Analysis ◽  
Incident Beam ◽  
Scanning Transmission Electron Microscope ◽  
Chemical Identification ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
General Method

The energy analysis of electrons scattered by a specimen in a scanning transmission electron microscope can improve contrast as well as aid in chemical identification. In so far as energy analysis is useful, one would like to be able to design a spectrometer which is tailored to his particular needs. In our own case, we require a spectrometer which will accept a parallel incident beam and which will focus the electrons in both the median and perpendicular planes. In addition, since we intend to follow the spectrometer by a detector array rather than a single energy selecting slit, we need as great a dispersion as possible. Therefore, we would like to follow our spectrometer by a magnifying lens. Consequently, the line along which electrons of varying energy are dispersed must be normal to the direction of the central ray at the spectrometer exit.

Phase behavior of cationic and anionic surfactants at low concentrations

1992 ◽  
Vol 50 (1) ◽  
pp. 694-695
Author(s):  
E. Naranjo
Keyword(s):  
Phase Behavior ◽  
Structural Characterization ◽  
Dynamic Systems ◽  
Anionic Surfactants ◽  
Intermolecular Forces ◽  
Stable Form ◽  
Surfactant Mixtures ◽  
Low Concentrations ◽  
Cationic And Anionic Surfactants ◽  
General Method

Equilibrium vesicles, those which are the stable form of aggregation and form spontaneously on mixing surfactant with water, have never been demonstrated in single component bilayers and only rarely in lipid or surfactant mixtures. Designing a simple and general method for producing spontaneous and stable vesicles depends on a better understanding of the thermodynamics of aggregation, the interplay of intermolecular forces in surfactants, and an efficient way of doing structural characterization in dynamic systems.

Caricaturing as a general method to improve poor face recognition: Evidence from low-resolution images, other-race faces, and older adults.

2019 ◽  
Vol 25 (2) ◽  
pp. 256-279 ◽  
Author(s):  
Amy Dawel ◽  
Tsz Ying Wong ◽  
Jodie McMorrow ◽  
Callin Ivanovici ◽  
Xuming He ◽  
...  
Keyword(s):  
Older Adults ◽  
Face Recognition ◽  
Low Resolution ◽  
General Method ◽  
Low Resolution Images

THE TEMPERATURE ROTATION OF THE EASY AXIS DIRECTION IN DyFe3

1979 ◽  
Vol 40 (C2) ◽  
pp. C2-193-C2-195 ◽  
Author(s):  
S. Japa ◽  
K. Krop ◽  
R. Radwanski ◽  
J. Wolinski
Keyword(s):  
Easy Axis ◽  
Axis Direction

Morphosemantic Analysis and Translation of Medical Compound Terms

1991 ◽  
Vol 30 (01) ◽  
pp. 30-35 ◽  
Author(s):  
P. Dujols ◽  
P. Aubas ◽  
C. Baylon ◽  
F. Grémy
Keyword(s):  
Medical Terms ◽  
General Method

This paper describes an automatic procedure for morphosemantic analysis and translation of compound medical terms. This analysis is of interest for the automatic indexation of medical discharge reports and summaries. Since words with the suffix -osis may have many different semantic interpretations, such -osis forms are taken as examples for a general method that avoids the difficulties in interpreting medical terms as reported in other studies.

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