Papers by Keyword: Magnetoelastic Coupling

Abstract: The matrix (5x5) Green's function of magnetoelastic waves in an isotropic magnetoelastic medium taking into account the dipole-dipole interaction has been derived. The imaginary parts of diagonal and off-diagonal elements of the Green's function in the crossing resonance of spin and longitudinal elastic waves has been investigated. It is shown that under changing the angle of wave propagation θ the amplitudes of Green functions change drastically due redistribution of energy between the magnetic and elastic oscillation. Approximate expressions for the dependence of the widths of the gaps in the spectrum on the angle θ have been also derived.

Abstract: The matrix Greens function of coupled spin and elastic waves for media with the 3D inhomogeneities of the coupling parameter is studied. It has been shown that the difference in shapes of the Greens functions for the cases of 1D and 3D inhomogeneities appears only for the sufficiently large correlation wave number of the inhomogeneities.

Abstract: We have investigated the chromium-iron alloy and compared it to the oxides α-Fe₂O₃ (E_g = 4.8eV) and α-Cr₂O₃ (E_g = 2.1eV). It is known that α-Cr₂O₃ and α-Fe₂O₃ both adopt a corundum-type structure, but display differences in the lattice constants, direct band gap, and magnetic ordering of the cations. The chromium-iron alloy was synthesized by thermal diffusion processes of both chromium and iron thin-films in air atmosphere conditions. We have studied the elastic distortions related to nature of the relative strains as well as magnetic coupling between Fe and Cr from the X-ray diffraction studies.

Abstract: Dynamic susceptibilities (Greens function) in a system of two wave fields of different physical nature connected by the zero-mean random coupling parameter are studied. Magnetoelastic waves in zero-mean magnetostrictive media are considered. It is shown that the Greens functions of the spin and elastic waves at the intersection of the initial dispersion laws have the form of broad single-mode peaks with the fine structure on the tops of these peaks: the narrow resonance on the top of and the narrow antiresonance on the top of . For the long-wave inhomogeneities the widths of the broad peaks and narrow peaks are determined by the root-mean-square fluctuation and the correlation wave number, respectively.

Abstract: The interaction between two wave fields of different nature that are caused by rms fluctuations of the coupling parameter between these fields in media with zero-mean coupling parameter is considered. Taking into consideration the multiple scattering processes of waves on the inhomogeneities leads to the results considerably different from those that have been obtained for the same situation in the Bourret approximation earlier [4,5]. Instead of the degeneration removal of frequencies in the wave spectrum and the appearance of two resonance peaks in the dynamic susceptibility at the intersection of the initial dispersion laws, the sharp broadening of the self-mode peak has to be observed. The consideration is done by the example of magnetoelastic waves in zero-mean magnetostrictive media.

Abstract: The role of magnetoelastic coupling in the mechanism of magnetically induced reorientation or redistribution (MIR) of twin variants is still a matter of some controversy. To evaluate this role ordinary magnetostriction of different Ni-Mn-Ga single crystals transforming to 5M (exhibiting MIR) and NM (no MIR) martensite were measured. The magnetostriction of Ni-Mn-Ga austenite is relatively low and steeply increases when approaching to martensite transformation. This is correlated to the softening of elastic modulus. Observed high field contribution of opposite sign may be due to the dependence of higher order elastic constant on magnetic field. The magnetostriction of martensite is difficult to determine as it is masked by much stronger MIR effect and indirect method must be used. The results are discussed in the frame of magnetoelastic model for MIR and compared with magnetic energy model.