Study on the coercivity and step effect of mixed magnetic films by micromagnetism and Monte Carlo simulation

Abstract

The magnetic properties of ferromagnetically and antiferromagnetically mixed fi lms are simulated by micromagnetism method based on the principle of energy mini mum and Monte Carlo technology. The hysteresis loops, spin configurations, and the influences of exchange constant JAA, uniaxial anisotropy constant K, dipolar interaction constant Dand diluted ratio of ferromagnetic ato m X on the coercivity Hc at the ground states are studied systematical ly for the systems studied. A t the same time, the temperature dependence of the coercivity is calculated. The simulated results indicate that: (1) a steplike hysteresis is evidently observed in the mixed magnetic films, and the result calculated by a simple Ising model reveals that the steplike effect can be attributed to the different response of the clusters with different size and different diluted ratio of antiferromagn etic atom on the external field; (2) at the ground states, as 0.5≤X≤1.0,the value of Hc increases with increasing values ofK, JAA, but decreases with increasing value of D; (3) a peak exists in the HcX curves. These simulated resu lts explain the experimental facts about the granular films with antiferromagnetic coupling. The T dependence of the value ofHc for the films with diffe rent magnitude of X can be well described by the law of Tα. But the value of α has a complex variation with the change of X.