High anisotropy alloy for thin film disk

Abstract

The thin film disk of the invention includes a thin film pre-seed layer of amorphous or nanocrystalline structure. The pre-seed layer, which may be CrTa or AlTi or AlTa, is deposited prior to a first crystalline layer. Although the pre-seed layer may be amorphous or nanocrystalline, for brevity it will be referred to herein as amorphous which is intended to encompass a nanocrystalline structure. In the preferred embodiment of the present invention, a pre-seed layer is sputtered onto a nonmetallic substrate such as glass, followed by a ruthenium-aluminum (RuAl) layer with B2 structure. The use of the pre-seed layer improves grain size and its distribution, in-plane crystallographic orientation, coercivity (Hc) and SNR. In a preferred embodiment of the present invention, the pre-seed layer is followed by the RuAl seed layer, a Cr alloy underlayer, an onset layer and a magnetic layer. The amorphous pre-seed layer also allows use of a thinner RuAl seed layer which results in smaller overall grain size, as well as, a reduction in manufacturing cost due to relatively high cost of ruthenium. The increased coercivity also allows the use of a thinner Cr alloy underlayer, which also results in smaller overall grain size. Another benefit lies in the fact that the pre-seed layer provides additional thermal conductivity, which could help prevent thermal erasures on a glass disk. A cobalt based magnetic layer with an optimal concentration of Pt, B and Cr is also used to form the magnetic layer. Such an optimization produces high anisotropy, low noise, high coercivity and smaller grain size of the magnetic layer.

Dependencies are inferred from the claim text.