Domain structure in biaxial Fe/Cr films induced by lateral fluctuations of the magnetic anisotropy

Abstract

The magnetic microstructure of single-crystalline Fe͑001͒ thin films has been studied by magnetic second harmonic generation and conventional magneto-optical Kerr effect methods. The layers were grown on GaAs/Fe/Ag͑100͒ substrates, capped by a Cr overlayer, and displayed a fourfold in-plane magnetic anisotropy. We observe the formation of a multidomain structure at magnetic fields ͉H͉ Յ 0.5 kOe, when the field is applied in a narrow range of azimuthal angles close to the hard axis direction ͉͑⌬͉ Ͻ 1°͒. The domains are characterized by the same longitudinal magnetization component M x and transverse components M y of opposite signs. We developed an approach to extract the change of the relative contributions of domains with different magnetization directions during magnetization reversal from the experimental data. The formation of a domain structure can be explained by taking into account the lateral fluctuations of the magnetic anisotropy energy caused by defects and stress at the interfaces and the role of the biquadratic exchange coupling between interfacial Fe and Cr magnetic moments.