Epitaxial bcc Fe has been grown on GaAs͑100͒-(4ϫ6) at room temperature and studied with in situ magneto-optical Kerr effect ͑MOKE͒, low-energy electron diffraction, and alternating gradient field magnetometry ͑AGFM͒. The magnetic properties at room temperature were found to proceed via three phases; a nonmagnetic phase for the first three and a half monolayers, a short-range-ordered superparamagnetic phase, and a ferromagnetic phase above about five monolayers. The thickness dependencies of the coercivity and MOKE intensity further suggested that the ferromagnetic phase is subdivided into three distinct regimes with different magnetic properties. A combination of the in situ MOKE and ex situ AGFM measurements shows that the entire Fe film is ferromagnetic with a bulklike moment after the onset of the ferromagnetism, in contrast with previous studies, in which magnetic dead layers or half-magnetization phases due to the intermixing of Fe and As were proposed. The results show that it is the growth morphology of the ultrathin films, rather than the diffusion of As, that plays the dominant role in determining the magnetic properties in this system.

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Articles you may be interested inComparison between the in-plane anisotropies and magnetostriction constants of thin epitaxial Fe films grown on GaAs and Ga 0.8 In 0.2 As substrates, with Cr overlayers J. Appl. Phys. 99, 08N508 (2006); 10.1063/1.2158974 Hysteretic properties of epitaxial Fe/GaAs(100) ultrathin films under external uniaxial strain J. Appl. Phys. 95, 6555 (2004); 10.1063/1.1676023 Study of in-plane magnetic anisotropy of ultrathin epitaxial Fe films grown on vicinal Mo(110) surface J. Appl. Phys. 95, 7312 (2004); 10.1063/1.1652411 Effects of step decoration by oxygen on ultrathin film magnetic anisotropy; p(1×1) Fe on vicinal W(100)The evolution of the uniaxial magnetic anisotropy of ultrathin epitaxial Fe films grown on InAs(100)-4ϫ2 and GaAs(100)-4ϫ2 has been studied in situ by means of the magneto-optical Kerr effect. In Fe/InAs͑100͒-4ϫ2, the uniaxial magnetic anisotropy easy axis direction along ͓011͔ was found to be rotated 90°compared with that of Fe/GaAs͑100͒-4ϫ2 along ͓01 1͔. Real-time reflection high energy electron diffraction measurements of Fe/InAs͑100͒-4ϫ2 show that the lattice constant of the epitaxial Fe films relaxes remarkedly faster along the ͓01 1͔ direction than along the ͓011͔ direction in the same thickness range where the uniaxial magnetic anisotropy occurs. These results suggest that the symmetry-breaking atomic scale structure of the reconstructed semiconductor surface gives rise to the uniaxial magnetic anisotropy in a ferromagnetic metal/ semiconductor heterostructure via surface magneto-elastic interactions.

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