Magnetooptical studies of the H–T phase diagram of an Fe/Si multilayered film

The magnetization reversal of a multilayered Fe/Si film having cubic magnetocrystalline anisotropy is investigated in the temperature interval 25–300 K by magnetooptical methods. It is found that the growth of the biquadratic exchange interaction as the temperature is lowered causes a spontaneous second-order phase transition from a collinear antiferromagnetic state to a noncollinear state. The presence of cubic anisotropy in the film gives rise to spontaneous and magnetic-field-induced first-order phase transitions between noncollinear states. Magnetooptical studies permit constructing the H–T magnetic phase diagram of the multilayered Fe/Si film for an orientation of the external field along the hard magnetization axis [110]. A calculation of the H–T phase diagram in the framework of a model taking into account the bilinear exchange and cubic anisotropy, with constants I1 and K that are assumed to be independent of temperature, and also the biquadratic exchange with a linearly temperature-dependent cons...