Physical reasons for the emergence of jumps during rotation of the magnetization of a two-sublattice ferrimagnet at low temperatures

It is shown that the contribution of the intersublattice exchange interaction to the magnetic anisotropy energy of a two-sublattice ferrimagnet can come only from higher order constants satisfying the condition 2K2+3K3+⋯>0. For this reason, for different signs of the first anisotropy constants of the sublattices, this contribution may cause a spontaneous spin-reorientation second-order transition, but not first-order transitions and jumps during magnetization rotation, which are associated with such a transition. Such jumps can appear only when the opposite inequality is satisfied, and the corresponding contribution to anisotropy can be ensured only by a fairly strong magnetoelastic interaction.