Two descriptions of magnetoelastic energy dissipation in uniaxial trigonal antiferromagnetic materials, associated with rotations of spontaneous magnetization of their sublattices

For trigonal siderite-type antiferromagnetic materials with allowance for the crystal symmetry considered in the thermodynamic potential, it is demonstrated that an amplitude dependence of the internal friction is observed in the absence of accompanying magnetic field along the [001] easy axis, whereas in the presence of the field, the amplitude-independent internal friction component is observed. In this case, it is expedient to use the ratio of energy dissipated for the period to oscillation energy as a measure of the internal friction for frequencies ω < τ⁻¹ (τ is the relaxation time), whereas for frequencies comparable with the Larmor frequency, the magnetic resonance phenomenon must be taken into account.