Effects of Ti doping on the magnetic and microstructure properties of the lower magnetic anisotropy CoCrPtRu-oxides layer in a perpendicular recording media

Abstract

Areal density capacity is constrained by linear and track density, and the recent advancements in magnetic layer structures have led to the development of segmented media. This configuration incorporates a graded magnetic anisotropy layer introduced through a non-magnetic exchange control layer. Optimizing this structural design yielded improvements in the signal-to-noise ratio (SNR) and an elevation in areal density capacity. To comprehensively investigate the magnetic properties and microstructure of the lower magnetocrystalline anisotropy constant (Ku) CoCrPtRu-oxides magnetic capping layer individually, we deposited the (0002) textured magnetic capping layer CoCrPtRu-oxides on (0002) Ru/NiW/NiTa underlayers. Additionally, metallic Ti was introduced into CoCrPtRu targets, replacing half of Ru, resulting in the deposition of the (0002) textured CoCrPtRuTi-oxides film was also deposited and compared to CoCrPtRu-oxides film. A comparative analysis was conducted between the CoCrPtRu-oxides and CoCrPtRuTi-oxides films. Microstructural image mapping and chemical composition analysis revealed that the introduced Ti in core grains diffused to the grain boundaries, enhancing grain separation. This diffusion was facilitated by the more negative formation energy of TiO2 (-3.512 eV/atom) compared with other oxides in the film. Consequently, the CoCrPtRuTi-oxides film exhibited slightly larger grain boundary areas (52%) and smaller grain sizes. Moreover, perpendicular coercivity (243.50 kA/m) and anisotropy were higher. This insight suggests a potential strategy for improving segregation by doping metallic elements, such as Ti, into the core grains, emphasizing the importance of not merely increasing the oxide content (e.g., TiO2).