Cooling field and temperature dependent exchange bias in spin glass/ferromagnet bilayers

Abstract

We report on the experimental and theoretical studies of cooling field (H<inf>FC</inf>) and temperature (T) dependent exchange bias (EB) in Fe<inf>x</inf>Au<inf>1-x</inf>/Fe<inf>19</inf>Ni<inf>81</inf> spin glass (SG)/ferromagnet (FM) bilayers. When x varies from 8% to 14% in the Fe<inf>x</inf>Au<inf>1-x</inf> SG alloys, with increasing T, a sign-changeable exchange bias field (HE) together with a unimodal distribution of coercivity (HC) are observed. Significantly, increasing in the magnitude of HFC reduces (increases) the value of HE in the negative (positive) region, resulting in the entire HE ∼ T curve to move leftwards and upwards. In the meanwhile, HFC variation has weak effects on HC. By Monte Carlo simulation using a SG/FM vector model, we are able to reproduce such HE dependences on T and HFC for the SG/FM system. Thus this work reveals that the SG/FM bilayer system containing intimately coupled interface, instead of a single SG layer, is responsible for the novel EB properties.