Isothermal tuning of exchange bias using pulsed fields

Abstract

Exchange bias, HE, and coercivity, HC, of antiferromagnetic (AFM)/ferromagnetic bilayers can be adjusted, after deposition, at temperatures below the Néel temperature of the AFM by subjecting the samples to large pulsed fields (in excess of HPulse=550 kOe). The efficiency of the process depends on the AFM system and the direction of the applied field with respect of the unidirectional anisotropy direction. Textured (111) Fe19Ni81/Fe50Mn50 bilayers show an HE reduction and a HC increase when the pulse field is applied antiparallel to the unidirectional anisotropy, while they only exhibit a reduction in HC when the pulse is applied parallel to their unidirectional anisotropy. On the other hand, textured (111) NiO/Co bilayers exhibit a change of the angular dependence of HE when the pulse is applied away from the unidirectional anisotropy. The effects could be caused by field induced changes in the domain structure of the AFM or transitions in the AFM (spin–flop or AFM–paramagnetic).