Intergranular magnetic coupling in CoNiCrPt and CoCrTaPt thin-film media characterized by the temperature dependence of the rotational hysteresis loss

In order to characterize intergranular magnetic coupling in (Co86Cr12Ta2)(100-x)Pt-x (x = 0 and 9) and (Co62.5Ni30Cr7.5)(100-x)Pt-x (x = 0 and 14) thin-film recording media, the temperature dependence of the rotational hysteresis loss has been examined. In all media, the coercive force H-c(T) gradually decreases to about half the value attained at 25 degrees C by increasing the measuring temperature T to about 300 degrees C without a change in the microstructure. In CoNiCr, CoNiCrPt and CoCrTaPt media, the decrease in H-c(T) with increasing T corresponds directly to the decrease in the magnetocrystalline anisotropy field of the grains, H-k(grain). In contrast, in CoCrTa media, H-c(T)/H-k(grain)(T) gradually decreases with increasing T. This decrease in H-c(T)/H-k(grain)(T) is suggested to be caused mainly by the increase in 4 pi M(s)(T)/H-k(grain)(T). This means that the intergranular magnetostatic coupling strongly affects the magnetic properties of the CoCrTa media examined here due to the low intergranular exchange coupling.