Simulation of the AC susceptibility for nano-ferromagnetic materials

Abstract

In this paper, the AC susceptibility of non-interacting random oriented nano-magnetic materials is studied by means of Landau-Lifshitz-Gilbert (LLG) equation, and temperature influence on the susceptibility are considered by introducing random fields. The results show that the AC susceptibility presents resonance behaviors in the alternating field. As the temperature increases, the resonance frequency of the system decreases monotonously. When the amplitude(H0) of the alternating field is small (H0 ≤ 0.02 Hr, where Hr is the resonance magnetic field in uniform reversal model), the resonance frequency is basically unchanged, however, when the amplitude of the alternating field is big (H0 > 0.02 Hr) , the resonance frequency decreases significantly as H0 increases. For different damping parameters, when the amplitude of alternating field is small, the amplitude of AC susceptibility decreases with the increase of damping parameters, but the resonance frequency changes little. When the amplitude of alternating field is big, the imaginary part of AC susceptibility and resonance frequency no longer change monotonously with the damping parameters. Based on the above results, we analyzed some experimental results of AC susceptibility of absorbing nanomaterials.