Improvement of magnetic intergranular isolation and evaluation of read/write characteristics on SmCo5 perpendicular magnetic thin films

Abstract SmCo 5 alloy is a promising candidate for ultra-high-density perpendicular magnetic recording (PMR) media because of its high uniaxial magnetocrystalline anisotropy K u of more than 1.1×10 8 erg/cm 3 . Previously, we successfully achieved high K u in a sputter-deposited SmCo 5 thin film by introducing a Cu/Ti dual underlayer. However, in order to apply the SmCo 5 films to practical PMR media, it is necessary to decrease medium noise. A granulated magnetic film comprising of small and magnetically decoupled grains is effective in reducing the medium noise. In this paper, we have proposed a new granular film that is fabricated by partial thermodiffusion of Cu between the Sm–Co continuous layer and the Cu underlayer, which is granulated using compositional segregation caused by the addition of Ta 2 O 5 . We have analyzed the magnetic properties, magnetic domain size, and magnetization reversal process of the proposed SmCo 5 film. The magnetic domain size decreased and the magnetization reversal process changed from the magnetic-wall-motion mode to a coherent rotation mode to some extent on isolation of magnetic grains. The read/write characteristics of granulated SmCo 5 double-layered media were also evaluated. The medium noise decreased and the signal-to-noise ratio increased for the granulated double-layered (PMR) medium.