Abstract
We report a systemeatic investigation of magnetic anisotropy of quaternary GaMnAsP ferromagnetic semiconductor films by magneto-transport. Hall measurements showed a transition of the easy magnetization direction from in-plane to out-of plane with incorporation of the P into the GaMnAs films. Quantitative information on magnetic anisotropy of the films is obtained by fitting the angular dependence of Hall resistance data to magnetic free energy using the coherent rotation model. Values of magnetic anisotropy parameters show that in-plane anisotropy decreases and out-of-plane anisotropy increases with increasing P content in these films. The out-of-plane magnetic anisotropy in GaMnAsP layers is further enhanced by low temperature annealing. By optimizing the growth and annealing conditions, we were able to obtain a Curie temperature of 125 K in such quaternary films, with strong out-of-plane anisotropy. This study showed that the magnetic anisotropy of the GaMnAsP films can be controlled by adjusting the concentration of the P, and by appropriate post-growth annealing.
Highlights
It is well established that incorporation of Mn ions in III-V semiconductors results in hole-mediated ferromagnetism, GaMnAs being the best-known example.[1,2,3,4] An important property of these ferromagnetic materials is their magnetic anisotropy, which determines the orientation of magnetization in the absence of magnetic field
To investigate magnetic anisotropy in our films, Hall resistance was measured with magnetic field applied perpendicular to the film, i.e., at θH = 0
The Hall resistance remains nearly constant during the rotation of a weak field, shown in Fig. 3(e) and (f), due to a strong magnetic anisotropy that locks the magnetization along one direction, so that it cannot be rotated by the applied field
Summary
It is well established that incorporation of Mn ions in III-V semiconductors results in hole-mediated ferromagnetism, GaMnAs being the best-known example.[1,2,3,4] An important property of these ferromagnetic materials is their magnetic anisotropy, which determines the orientation of magnetization in the absence of magnetic field. The easy direction of magnetization in III-Mn-V films can either be in-plane or out-of-plane, depending on strain conditions arising from lattice mismatch between the III-Mn-V layer and the substrate on which it is grown. In GaMnAs the easy axis of magnetization is in-plane under compressive strain, and out-of-plane under tensile strain.[5,6] The most extensively studied case is that of GaMnAs grown directly on GaAs, where the GaMnAs layer is compressively strained, exhibiting in-plane magnetic easy axes. Since the incorporation of P into the GaMnAs lattice reduces the lattice parameters below that of GaAs, 055809-2 Lee et al
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