Dependence of exchange bias in Ni sub 81 Fe sub 19 /Pt sub x Mn sub 1-x (0 < x < 0.2) bilayers on composition and microstructure

The exchange coupling between ferromagnetic Ni sub 81 Fe sub 19 and antiferromagnetic Pt sub x Mn sub 1-x , films prepared by RF magnetron sputtering has been investigated. The study has focused on the relationship between the exchange bias and the structural characteristics of the Pt sub x Mn sub 1-x films, such as crystallinity, texture, and granularity. The Pt content of the Pt sub x Mn sub 1-x film is in the range of 0 at% < x < 20 at%. The exchange bias in this system is associated with the stabilization of the gamma -phase with a disordered FCC structure in the Pt sub x Mn sub 1-x films. Although the texture of the polycrystalline Pt sub x Mn sub 1-x films improves with increasing Pt content, a relatively large exchange field of 64Oe at room temperature and a high blocking temperature of about 200 deg C were found in Ni sub 81 Fe sub 19 (15 nm)/Pt sub 8 Mn sub 92 (30 nm). The exchange bias of the of Ni sub 81 Fe sub 19 /Pt sub x Mn sub 1-x bilayers is dependent on the intrinsic properties of the Pt sub x Mn sub 1-x films, such as the exchange coupling between the antiferromagnetic moments and the magnetocrystalline anisotropy, which decrease with the Pt doping concentration.