Angular dependence of the pinning fields for hard/soft multilayers

The exchange-coupled hard/soft magnetic material, proposed in 1991 by Kneller et al., is widely regarded as an excellent next-generation permanent magnetic material. A perfect composite material is expected to hold a large energy product because of the combination of the large remanence of the soft phase and the high coercivity of the hard phase. A giant energy product as high as 120 MG Oe was thus predicted by Skomski and Coey in 1993. However, experimental values are much smaller, where easy axis deviations are found to be an important factor leading to the outstanding discrepancy. In the meantime, the magnetic reversal mechanism also varies with β, the angle between the easy axis and the applied field. In this work, hysteresis loops and energy products have been calculated for hard/soft multilayers with various β based on a self-contained micromagnetic model, focusing on the angular dependent magnetic reversal mechanism.