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° domain walls and which gives a classic square hysteresis loop, or by a ‘‘2-jump’’ mechanism, by the sweeping of 90° 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.

Low temperature oxidation mechanisms of nanocrystalline magnetite thin film J. Appl. Phys. 113, 013510 (2013) In situ control of electronic phase separation in La1/8 Pr4/8Ca3/8MnO3/PNM-PT thin films using ferroelectricpoling-induced strain J. Appl. Phys. 113, 013705 (2013) Spin precession modulation in a magnetic bilayer Appl. Phys. Lett. 101, 262406 (2012) Alternating domains with uniaxial and biaxial magnetic anisotropy in epitaxial Fe films on BaTiO3 Appl. Phys. Lett. 101, 262405 (2012) Additional information on J. Appl. Phys. We have studied the evolution of the magnetic in-plane anisotropy in epitaxial Fe/GaAs films of both ͑001͒ and ͑110͒ orientation as a function of the Fe layer thickness using the longitudinal magneto-optic Kerr effect and Brillouin light scattering. Magnetization curves which are recorded in situ during film growth reveal a continuous change of the net anisotropy axes with increasing film thickness. This behavior can be understood to arise from the combination of a uniaxial and a cubic in-plane magnetic anisotropy which are both thickness dependent. Structural analysis of the substrate and Fe film surfaces provides insight into the contribution of atomic steps at the interfaces to the magnetic anisotropy. Changing the degree of crystalline order at the Fe-GaAs interface allows us to conclude that the magnetic anisotropies are determined by atomic scale order.

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