Training Induced Positive Exchange Bias in NiFe/IrMn Bilayers

TL;DR

This study reports the observation of positive exchange bias in NiFe/IrMn bilayers after magnetic training, revealing a new phenomenon linked to metastable magnetic disorder at the interface.

Contribution

It introduces a novel magnetic training effect where positive exchange bias emerges after successive magnetization reversals in NiFe/IrMn bilayers.

Findings

Positive exchange bias observed after training.

Training removes initial negative bias.

Effect persists down to 30 K below blocking temperature.

Abstract

Positive exchange bias has been observed in the Ni$_{81}$Fe$_{19}$/Ir$_{20}$Mn$_{80}$ bilayer system via soft x-ray resonant magnetic scattering. After field cooling of the system through the blocking temperature of the antiferromagnet, an initial conventional negative exchange bias is removed after training i. e. successive magnetization reversals, resulting in a positive exchange bias for a temperature range down to 30 K below the blocking temperature (450 K). This new manifestation of magnetic training is discussed in terms of metastable magnetic disorder at the magnetically frustrated interface during magnetization reversal.