In-plane volume and interface magnetic anisotropies in epitaxial Fe films on GaAs(001)

Epitaxial Fe alms were grown on Ga-terminated GaAs(0 0 1) surfaces by molecular beam epitaxy. Samples with constant Fe thickness as well as step patterned Fe films have been studied. In-plane magnetic anisotropy energies were determined from hysteresis loops measured by alternating gradient magnetometry and magneto-optic Kerr effect. A superposition of anisotropies with fourfold and uniaxial symmetry was found in all films. From the linear variation of both contributions with the inverse Fe thickness, the volume and the interface term are determined. The fourfold anisotropy constant of the Fe/GaAs(0 0 1) interface amounts to -(1.41 +/- 0.2) x 10(-2) erg/cm(2). As a consequence, the easy and hard directions of the fourfold term are rotated by 45 below 6 ML. The uniaxial anisotropy turns out to be a pure interface term originating exclusively from the Fe/GaAs interface. The huge anisotropy constant, K(U)(Fe/GaAs) = (1.2 +/- 0.2) x 10(-1) erg/cm(2), produces an in-plane anisotropy field up to 2 kOe. (C) 1999 Elsevier Science B.V. All rights reserved.