Dynamic enhancement of the exchange bias training effect

Abstract

Exchange bias in coupled magnetic thin films and its accompanying training effect are fundamental interface phenomena with significant impact in spintronic applications. Both effects are well known in heterosystems of ferro- and antiferromagnetic thin films. Here, we report on the dynamic enhancement of the training effect in an exchange coupled bilayer of soft and hard ferromagnetic materials. Training is referred to as a gradual change of the bias field, which evolves upon cycling the soft layer through consecutive hysteresis loops. Its dynamic enhancement is observed with increasing sweep rate of the applied magnetic field from quasistatic to the fully dynamic range. A dynamically generalized theory based on triggered relaxation is in excellent agreement with the training data. Additionally, we evidence the remarkable universality of our theoretical approach when applying it to the dynamically altered training effect of a conventional exchange bias system involving an antiferromagnetic pinning layer.