We present an experimental and theoretical study on the origin of the strong in-plane uniaxial magnetic anisotropy in (Ga,Mn)As layers, unexpected from the cubic crystalline structure. The symmetry lowering can be accounted for by structural or effective shear strains. We find theoretically out-of-plane and in-plane magnetic anisotropy constants being linear with the shear strain. Searching for a real shear strain arising from lattice relaxation, we perform two types of measurements: anomalous x-ray diffraction and strain-induced optical birefringence, at room temperature. Working on a strongly anisotropic (Ga,Mn)As layer, the estimated was not found although it lied an order of magnitude above the detection threshold. This ensemble of results indicates as unlikely a relaxation-driven uniaxial anisotropy. As previously suggested theoretically, the magnetic symmetry-lowering could instead originate from the anisotropic incorporation of Mn atoms during growth. This would yield a perfectly in-plane matched lattice, with an anisotropy that could nevertheless be modeled as an effective shear strain and modified by an external shear stress, in agreement with the existing experimental literature.
Exploring the shear strain contribution to the uniaxial magnetic anisotropy of (Ga,Mn)As
M. Kraimia, L. Largeau, K. Boujdaria, B. Croset, C. Mocuta, A. Lemaître, C. Gourdon, L. Thevenard; Exploring the shear strain contribution to the uniaxial magnetic anisotropy of (Ga,Mn)As. J. Appl. Phys. 7 March 2020; 127 (9): 093901. https://doi.org/10.1063/1.5140078
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