Monte Carlo modeling of magnetic properties in magnetic granular films for high-density recording

Abstract

In this paper, magnetic properties of Co-C and CoPt-C nanogranular films are modeled using the Monte Carlo method. Each grain in the films is assumed to be spherical in shape, with a single domain and a random crystalline easy axis in the model. For Co-C films, the hysteresis loop for hexagonal close-packed(hcp)Co grains of 3 nm in size is calculated at various temperatures ranging from 3 K to 300 K. The superparamagnetic relaxation blocking temperature(T_B)is demonstrated to be about 20 K. For CoPt-C films, hysteresis magnetization calculations are performed on face-central-tetragonal(fct)CoPt inter-metal compound grains encapsulated in carbon with various grain sizes ranging from 4 nm to 6 nm and different distributions. Extremely high coercivities required by ultra-high density magnetic recording are achieved in these films owing to the very large anisotropy of fct CoPt compound. The numerical results are compared with our experimental data of Co-C granular films and those of CoPt-C granular films recently reported in the literatures.