Magnetic switching and in-plane uniaxial anisotropy in ultrathin Ag/Fe/Ag(100) epitaxial films

We have studied the process by which the in-plane magnetization of an ultrathin (4-11 ML) epitaxial iron film reverses under the action of an external magnetic field. Kerr effect measurements reveal a small in-plane uniaxial anisotropy superimposed on the cubic magnetocrystalline anisotropy which greatly influences the reversal. In addition, we find that depending upon the field orientation, reversal can proceed either via a ''1-jump'' mechanism, by the sweeping of 180 degrees domain walls and which gives a classic square hysteresis loop, or by a ''2-jump'' mechanism, by the sweeping of 90 degrees domain walls at two distinct applied field strengths-this gives a more unusual hysteresis loop with two irreversible transitions. We have developed a simple phenomenological energy model which explains how so small a uniaxial anisotropy can play so significant a role in the reversal process. The model explains the two reversal mechanisms and predicts with good experimental agreement which should be observed for different applied field orientations. (C) 1995 American Institute of Physics.