INVESTIGATION OF ELECTROMAGNETIC SHOCK-WAVE STRUCTURE IN ANISOTROPIC FERROMAGNETS WITH EASY-AXIS

Shock waves and their structure are investigated in anisotropic ferrom agnets with an easy axis of magnetization. For anisotropy of this type , shock (Hugoniot) adiabat, evolutionary conditions, and condition of nondecreasing entropy are obtained. The Landau-Lifshitz equation with dissipation term is used to describe the structure. The set of admissi ble discontinuities (i.e. those possessing the structure) does not coi ncide with the set of a priori evolutionary discontinuities. As shown in a set of figures that set of admissible discontinuities is a dashed line on a priori evolutionary intervals (with very short dashes and s hort intervals between them), and a set of isolated points on one of a priori nonevolutionary intervals of the shock adiabat. The distance b etween points is of the same order as the length of the dashes mention ed above and is determined by the ratio of dissipation and dispersion inside the structure of the shock wave. Each of these points on the sh ock adiabat corresponds to the discontinuity with a specified velocity , that from this point of view is similar to the deflagration front in gasdynamics. The investigation is numerically supported, and concrete examples of these points are found and the number of points is estima ted. Similar results were obtained earlier by qualitative methods in t he case of small angles between the field and the normal to the wave f ront [N.I. Gvozdovskaya, A.G. Kulikovskii, About electromagnetic waves and their structure in anisotropic magnets, J. Appl. Math. Mech. (Pri kl. Mat. Mekh.) 61 (1) (1997) 135-143]. (C) 1999 Elsevier Science B.V. All rights reserved.