Exchange-bias training effect inTbFe∕GdFe: Micromagnetic mechanism

Abstract

We present magnetization and Kerr microscopy measurements of the exchange-bias training effect in hard/soft, ${\mathrm{Tb}}_{12}{\mathrm{Fe}}_{88}$/${\mathrm{Gd}}_{40}{\mathrm{Fe}}_{60}$, bilayers. These experimental results, compared with micromagnetic simulations, unambiguously show the role of the soft GdFe layer reversal on irreversible magnetic changes in the hard TbFe layer. After a partial reversal of the GdFe magnetization layer, the next field cycle exhibits a double hysteresis loop which is due to the existence of two types of domains in the sample, and only one of these domains has been subject to the training effect. The antiferromagnetically interfacial coupling and positive exchange-bias shift permit us to exclude any direct contribution from the magnetic field to this mechanism.