Magnetic susceptibility of ferromagnets at the spin-flop phase transition

The dynamic properties of a uniaxial ferromagnet are studied in the vicinity of the spin-flop phase transition, with allowance for the isotropic magnetostriction. The spectrum and the polarization of coupled magnetoelastic waves are found and so is the magnetic susceptibility tensor χ. For selected directions of the wave vector k and polarizations on the astroid (where the metastable magnetization vanishes), the phase velocity of the long-wave sound tends to zero and its attenuation increases. At lower frequencies the value k = 0 is an essential singular point of the function χ^(k). The magnetic susceptibility components have singularities on the the astroid only along those directions of k on which “softening” of the phonon mode occurs.

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