DIRECT MEASUREMENT OF SUBNETWORK EXCHANGE COUPLING-CONSTANT FOR FERRIMAGNETS

We show that the subnetwork exchange coupling constant lambda of ferrimagnetic films is equal to the slope of the plot of the magnetic field H applied in the film plane versus the in-plane magnetization M(parallel-to) at compensation temperature T(comp), i.e. H=lambdaM(parallel-to) at T(comp). This finding enables the direct measurement of lambda for ferrimagnetic magneto-optical recording thin films, regardless of the complexity of the two-subnetwork problem. The experimental results are within the range predicted by the mean-field theory.