Exchange bias anisotropy versus antiferromagnet thickness in uniaxial Cr/Fe bilayers

Abstract

We have investigated the thickness dependence of exchange bias ͑EB͒ in ultrathin epitaxial Cr/Fe/Ag͑001͒ bilayers. The system features an artificially patterned structure consisting of coherently aligned nanometric ripples at the Cr/Fe buried interface. The patterning provides an abundance of preferentially aligned steps resulting in both morphological and magnetic uniaxial anisotropies. Increasing the Cr thickness the EB evolves from an uniaxially anisotropic state, in which its magnitude is a function of the field-cooling direction, to an isotropic behavior. We account for this phenomenon invoking a thickness-dependent variation in the spin structure of the antiferromagnet driven by the topological frustration at the stepped Cr/Fe interface.

Model of exchange bias in a trilayer FM/AFM/FM structure

“…17 But in this case the properties of the hysteresis loops (horizontal plateau, canted regions of the curve and splitting of the hysteresis curve) are preserved. 17,18 It is necessary to remember that above we have examined a case of an odd number of layers in the AFM film (Fig. 1).…”