Magnetic Excitations in Locally Non-Equilibrium Continuum

Abstract

On the basis of locally non-equilibrium thermodynamics the equation for dynamics of the magnetic moment vector is derived. For a magneto disordered continuum the spectrum of locally non-equilibrium uctuations is determined. It is shown that the spectrum is composed of electromagnetic-spin branches, which contain energy gaps and spin-electromagnetic ones which do not. Unstable modes in diamagnets are found. The dispersion relation and frequency dependence of the damping coecient are determined for coupled waves of the magnetic vector potential and magnetization. It is shown that there exist frequency regions of transmission and non-transmission. Frequencies of the undamped waves and constant-phase damped waves can be located in these regions.

Locally Non-Equilibrium Magnetoelectric State in Diamagnetic

“…The constitutive equation takes into account the medium's memory, the causality principle and spatial dispersion. The kinetic coefficients satisfy the symmetric equations [5]. In addition, positivity of the form (3) requires the positivity of the principal minors of the matrix I nm (I nn > 0, I nn I n+1,n+1 − I n,n+1 I n+1,n > 0 and further) [10].…”

“…). For a < 0, the region of instability begins with q = 0 [5] and, consequently, the ground state is ferromagnetic with the magnetization M 2 s = −a/2a . We confine ourselves to the cubic nonlinearity in the defining relations.…”

“…In Refs. [5,6] the equation of magnetization motion was obtained on the basis of locally non-equilibrium thermodynamics [7,8] by analogy with hydrodynamics [9]. In the last equation, the surface and bulk moments of forces that are not local in time and space are taken into account.…”

“…In the last equation, the surface and bulk moments of forces that are not local in time and space are taken into account. On the basis of this equation, locally nonequilibrium waves of magnetization in a disordered dielectric continuum were considered [5,6]. In the diamagnetic state, unstable modes were observed in the region of large wavenumbers.…”