Search

The thermal stability and the atomic ordering of single-crystal Heusler alloy Co2FeSi layers grown by molecular beam epitaxy on GaAs(001) have been studied. We found that the Co2FeSi layers have a long-range atomic order and crystallize in a partly disordered L21 structure in the low growth temperature (TG) regime. The long-range atomic order of the layers is further improved with increasing TG up to 350 °C. However, the increase of TG induces an interfacial reaction between the Co2FeSi layer and the GaAs substrate. The analysis of the in-plane magnetic anisotropy reveals that the interface perfection is improved up to TG=200 °C and deteriorated due to an interfacial reaction above 200 °C. [ABSTRACT FROM AUTHOR]

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 100 nm (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 [33???] and [???10], respectively, whereas samples of thickness dFe ⩾ 70 MLs exhibit a dominating four-fold magnetic anisotropy with the easy axes along the in-plane ⟨03??⟩ directions. The reorientation of the easy axis from [33???] to the in-plane ⟨03??⟩ 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 Keffu 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 Keff1 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. [ABSTRACT FROM AUTHOR]

Structural, electrical, and magnetic properties of Fe3Si/GaAs(113)A hybrid structures are studied, dependent on the layer composition varying from 15 to 26 at. % Si. The presence of superlattice reflections in x-ray diffraction and lower resistivity confirms the long-range atomic ordering in the stoichiometric Fe3Si films, reflecting the D03 crystal structure. The observed atomic ordering is also found to influence the sign and magnitude of the antisymmetric component of the planar Hall effect observed in this orientation. However a finite disorder is observed even in nearly stoichiometric samples. [ABSTRACT FROM AUTHOR]

We have studied the thickness dependence of the structural and magnetic properties of ultrathin Fe3Si films grown on GaAs(001). The onset of ferromagnetism is found to be at about 3 ML at low temperatures. Furthermore, a reorientation of the uniaxial in-plane magnetic anisotropy takes place when the thickness of the films is reduced. This is due to a competition between a volume term and an interface contribution, which have opposite sign. Whereas the origin of the volume term remains unclear, the interface contribution is attributted to an anisotropic bonding at the Fe3Si/GaAs(001) interface, similar to other ferromagnet/semiconductor hybrid structures. [ABSTRACT FROM AUTHOR]