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 (Co86Cr12T a2)(100-x)Pt-x (x = 0 and 9) and (Co62.5Ni30Cr7.5)(100-x)Pt-x (x = 0 a nd 14) thin-film recording media, the temperature dependence of the ro tational 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 de grees C without a change in the microstructure. In CoNiCr, CoNiCrPt an d CoCrTaPt media, the decrease in H-c(T) with increasing T corresponds directly to the decrease in the magnetocrystalline anisotropy field o f the grains, H-k(grain). In contrast, in CoCrTa media, H-c(T)/H-k(gra in)(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 magnetostati c coupling strongly affects the magnetic properties of the CoCrTa medi a examined here due to the low intergranular exchange coupling.