Evolution of magnetic anisotropy and spin-reorientation transition in Fe films grown on GaAs(113)A substrates by molecular-beam epitaxy

Abstract

The magnetic properties of Fe films grown on GaAs(113)A substrates by molecular-beam epitaxy are studied using superconducting quantum interference device magnetometry for a wide range of thickness varying from 3.5 monolayers (MLs) to 100nm (714 MLs). The first signature of ferromagnetism is found at a nominal coverage of about 4 MLs, attributed to a percolation phenomenon, similar to Fe on GaAs(001). The magnetic anisotropy of all samples is found to be a combination of varying strengths of an in-plane uniaxial magnetic anisotropy (UMA) and a four-fold magnetic anisotropy. Samples of thickness dFe⩽50 MLs exhibit a dominating UMA with the easy and hard axes along [332¯] and [1¯10], respectively, whereas samples of thickness dFe⩾70 MLs exhibit a dominating four-fold magnetic anisotropy with the easy axes along the in-plane ⟨031¯⟩ directions. The reorientation of the easy axis from [332¯] to the in-plane ⟨031¯⟩ axes is found to take place between 50 and 70 MLs, the same thickness range where the relaxation of the layer starts. The effective uniaxial magnetic anisotropy constant Kueff first increases with monolayer coverage up to about 10 MLs and then decreases with the increase in thickness. On the other hand, the effective four-fold anisotropy constant K1eff first increases with monolayer coverage and then saturates close to the bulk value after about 20 MLs. From a comparison of our results with literature a common origin of UMA in Fe films on GaAs(001) and (113)A, i.e., the anisotropy of the bonding of Fe with As and Ga at the interface is anticipated.