Hexagonal Closed Packed CoPtRu Alloy as a Buffer Layer Material for Promoting Heteroepitaxial Growth for Perpendicular Magnetic Recording Media

Abstract

Crystal structure and magnetic properties for Co–Pt–Ru alloy films and Co–Pt–Ru–oxide granular films were investigated for material to reduce the lattice mismatch between the magnetic layer and the nuclei control layer of the perpendicular magnetic recording media. The laminate stacking structure of the sample was sub/NiFeCr (20 nm)/Ru (20 nm)/Co–Pt–Ru (20 nm). The amount of stacking faults in the films was evaluated as a probability of occurrence of fcc stacking, Pfcc measured by an in-plane X-ray diffractometry profile. As a result, it was found that: 1) hcp atomic stacking structures of the Co100– x Ru x alloy films were stable compared with that of Co100– x Pt x alloy films for almost all of the additional content x; 2) lattice constant a and c for Co–Pt–Ru ternary alloy film could be controlled between 2.51 to 2.59 A, and 4.07 to 4.41 A, as changing the Pt and Ru content with a total amount of 0 to 50 at.%, respectively. And the lattice constant ratio c/a decreased from 1.62 to 1.59 with increasing Ru content more than 20 at.%; 3) Pfcc in the Co–Pt–Ru ternary alloy films was less than 0.5% for the samples with Ru content were more than 20 at.%; 4) uniaxial magnetocrystalline anisotropy K u could be controlled from 12.6 to 0 106 erg/cm3 by adding Pt and Ru with a total amount of 30 at.% to a Co75Pt25 film; and 5) Co–Pt–Ru–(SiO2) film with the columnar structure was realized for Ar gas pressure of 4 Pa during sputtering.