EXCHANGE COUPLING AND ENERGY PRODUCT IN RANDOM 2-PHASE ALIGNED MAGNETS

Size effects in two-phase Boolean magnets composed of an aligned hard phase and a sort phase with high magnetization are investigated. In 'overcritical' magnets, where the size of the soft regions is larger than the Bloch-wall width delta(h) of the hard phase, the energy product is reduced compared to the corresponding 'undercritical' magnets with small soft regions, where theoretical energy products as high as 1 MJ/m3 have been predicted. Nevertheless, the theoretical energy product only gradually drops with increasing size of the soft regions, and it may still exceed the theoretical energy product 516 kJ/m3 of Nd2Fe14B.