The dependence of direct overwrite characteristics on the magnetic properties of DC magnetron sputtered films

The magnetization of rare-earth transition metal films was varied by changing the compensation and the Curie temperatures independently. The coercivity was varied by depositing films with different thicknesses and with an underlayer of silicon nitride. The direct overwrite characteristics investigated include the minimum pulsewidth for erasing and writing a certain size domain, the pulsewidth margins for erase, and the erasable size of domain. The minimum pulsewidth for erasing domains increases when the film thickness increases or an underlayer of silicon nitride is deposited between the magnetic layer and its glass substrate. The poorer erasure performance is due presumably to the higher coercivity at high temperatures in the thinner films. A decrease in the compensation temperature leads to an increase in the magnetization of high temperatures and causes the minimum erasure pulsewidth to increase and the largest erasable domain size to decrease.