Comparison on the structure and exchange bias in Co/MnPt and MnPt/Co polycrystalline films on glass substrates

Abstract

Structure and magnetic properties of sputter-prepared Co(5 nm)/MnPt(20 nm) and MnPt/Co polycrystalline films with various annealing temperatures (T) have been compared. XRD and TEM analysis show that MnPt is more compressive in film plane for Co/MnPt than MnPt/Co at as-deposited state. Large H E of 464-560 Oe are attained in two series films through proper thermal process of post annealing and cooling in external magnetic field. The increase of H E with T is mainly dominated by the ordering degree of MnPt layer and the roughness of the interface. As compared to MnPt/Co film (T = 250 ○ C), Co/MnPt film with more compressive in film plane exhibits L1 0-ordering, the onset of stress release, and the optimized H E at lower T = 200 ○ C. Higher H E for MnPt/Co film at T = 250 ○ C (560 Oe) than Co/MnPt film T = 200 ○ C (464 Oe) might be related to grain growth for L1 0 phase. Nevertheless, higher annealing temperature leads to the interdiffusion, the roughened surface and therefore the decrease of H E and Hc. This study provides useful information to fabricate exchange-bias system with L1 0-MnPt as an antiferromagnetic layer.