Exchange biasing in as-prepared Co/FeMn bilayers and magnetic properties of ultrathin single layer films

For Co and CoNi single layer films, the coercivity is a linear function of the inverse layer thickness and has an angular dependence of a fourfold-like symmetry although only a uniaxial anisotropy exists. For both as-prepared and post field-cooled Co/FeMn bilayers, the exchange field and the coercivity enhancement are proportional to the inverse Co thickness. For as-prepared ones, the exchange field and the coercivity are smaller than those of post field-cooled ones. At the same time, the exchange field, the coercivity, and the in-plane resonance field have the similar angular dependence as those of post field-cooled ones. The magnetization reversal process must be accompanied by non-coherent rotation model in Co and CoNi single layer films, and as-prepared Co/FeMn bilayers.