Micromagnetic Study of the Complex Transverse Susceptibility of Uniaxial Ferromagnets With Quartic Anisotropy

A micromagnetic model based on critical curves formalism for the complex transverse susceptibility (TS) of particulate media, for very low values of the frequency of the ac field, is presented. The effect of higher order terms in the uniaxial anisotropy energy series expansion and the effect of the amplitude of excitatory ac field are taken into account. When second order term is present in the uniaxial anisotropy energy ground state can change from easy-axis to easy-cone type and a complex energy profile is generated. It is shown that additional Barkhausen jumps driven by higher-order anisotropy constants can give rise to an imaginary part of TS