Systematic study of in-plane magnetic anisotropy in CoCrPtB/Cr media

Abstract

Circumferential texturing in longitudinal recording media induces in-plane magnetic anisotropy. It is characterized by orientation ratio (OR), which is an important parameter affecting media performance. Our work shows that among the media with different OR values (including isotropic media with OR=1), the ones with higher OR have both better thermal stability and better recording performance. Therefore, it is important to have a better understanding of the mechanism for in-plane anisotropy so that OR can be further increased. Several mechanisms for in-plane anisotropy have been proposed through micromagnetic analysis or empirical methods. A systematic study of OR in CoCrPtB/Cr media was performed to explore the mechanism of in-plane magnetic anisotropy. Circumferential texture roughness has the most effect on OR, but OR is also strongly affected by magnetic alloy composition and sputtering process parameters such as substrate temperature, underlayer thickness, and magnetic-layer thickness. Higher substrate temperature, thinner underlayer thickness, and thinner magnetic-layer thickness all lead to higher OR. These results suggest that the in-plane magnetic anisotropy comes from stress anisotropy via the inverse magnetostriction effect. The stress is induced at the magnetic-layer/underlayer and underlayer/substrate interfaces, while the anisotropy is suggested to arise from the topology of the circumferential texture lines.