An expression is obtained for the Feynman path integral in the case of Fermi systems with covariant symbol of the Hamiltonian of arbitrary Grassmann parity.

Feynman principle for fermions with odd covariant symbol of the Hamiltonian

Polarization of nonlinear magnetoacoustic waves in ferromagnets

The nonlinear coherent interaction of a high‐frequency acoustic wave pulse with a magnetically ordered medium is studied theoretically. We consider both microscopic and phenomenological theories of the formation of nonlinear magneto‐acoustic waves in a ferromagnet. A self‐consistent determination of the dispersion law for nonlinear magneto‐acoustic waves in a ferromagnet is carried out. It is shown that in both of these theories nonlinear excitations arise which can be of the form of a periodic nonlinear wave, a soliton, or a kink. The nature of the change of polarization of transverse linearly polarized magneto‐acoustic waves is also investigated.

Nonlinear magneto‐acoustic waves in ferromagnets

A theoretical investigation is made of the nonlinear coherent interaction of an elastic wave pulse with a Heisenberg ferromagnet. It is shown that in such a situation nonlinear waves, which may have the form of a periodic nonlinear wave, a soliton, and a kink, are formed. The dispersion law for these waves is determined. The possibility of experimental observation of the predicted nonlinear phenomena is discussed.

G. T. Adamashvili

Papers

Nonlinear waves in ferromagnets