Correlation between perpendicular exchange bias and magnetic anisotropy in IrMn/[Co/Pt](n) and [Pt/Co](n)/IrMn multilayers

Abstract

Perpendicular exchange bias has been observed for IrMn/[Co/Pt]n and [Pt/Co]n/IrMn multilayers in the as-deposited state. The exchange bias field is largest when the IrMn film is grown on magnetically saturated Co/Pt multilayers (8.12 mT for n = 3), whereas it is considerably smaller when domain formation in the IrMn film occurs before Co/Pt deposition (3.30 mT for n = 3). After annealing at 220 °C in an out-of-plane magnetic field the perpendicular exchange bias field and magnetic anisotropy are considerably larger for the Co/Pt multilayers with an IrMn film at the bottom. The apparent correlation between bias and anisotropy is explained by the dependence of the perpendicular exchange bias field on the orientation of the Co spins near the Co/IrMn interface.