Perpendicular anisotropy of a-FeTbGd and CrCo alloys deduced from torque measurements

CrCo and amorphous FeTbGd are two potential media for perpendicular magnetic recording. In order to compare their properties, VSM hysteresis loops were plotted and torque measurements carried out. CrCo media present a very high saturation magnetization and a low squareness as compared to a-FeTbGd. On the other hand torque curves measured or a-FeTbGd are typical of an easy axis perpendicular to the film plane, which is not the case for the CrCo samples. Nevertheless the intrinsic perpendicular uniaxial perpendicular energy is larger for CrCo samples than for a-FeTbGd. The differences in the perpendicular behaviour between the two media are attributed to the quality factor which can be very large for a-FeTbGd as compared to CrCo. Since the saturation field is equal to coercivity for a-FeTbGd media and can be obtained with heads used nowadays it is suggested that the achievement of high density mass disk memories could be easier with a-FeTbGd than CrCo.