Micromagnetic Studies at Finite Temperature on FePt-C Granular Films

A new micromagnetic method using the hybrid Monte Carlo (HMC) algorithm has been developed, and the magnetic properties at finite temperature can be simulated. In this paper, the HMC micromagnetics are applied on the polycrystalline FePt-C granular films for heat-assisted magnetic recording, where the significant parameters such as the temperature-dependent saturation magnetization M_s(T) are measured by experiments. The Voronoi polycrystalline microstructure is built upon a regular mesh of micromagnetic cells. The magnetization (M-H) loops below the Curie temperature are calculated; they agree well with experiments at 300, 400, 500, and 600 K, respectively, which have confirmed the validity of the HMC micromagnetic method. Besides, the M-H loop at 700 K, which currently cannot be measured by experiments, can also be simulated using the HMC algorithm, which shows superparamagnetic properties.