Strain control of magnetic anisotropy in (Ga,Mn)As microbars

Abstract

We present an experimental and theoretical study of magnetocrystalline anisotropies in arrays of bars patterned lithographically into (Ga,Mn)As epilayers grown under compressive lattice strain. Structural properties of the (Ga,Mn)As microbars are investigated by high-resolution X-ray diffraction measurements. The experimental data, showing strong strain relaxation effects, are in good agreement with finite element simulations. SQUID magnetization measurements are performed to study the control of magnetic anisotropy in (Ga,Mn)As by the lithographically induced strain relaxation of the microbars. Microscopic theoretical modeling of the anisotropy is performed based on the mean-field kinetic-exchange model of the ferromagnetic spin-orbit coupled band structure of (Ga,Mn)As. Based on the overall agreement between experimental data and theoretical modelling we conclude that the micropatterning induced anisotropies are of the magnetocrystalline, spin-orbit coupling origin.

Effect of lithographically-induced strain relaxation on the magnetic domain configuration in microfabricated epitaxially grown Fe81Ga19

“…1(c) , reveals that there is a nonzero strain relaxation in the centre of the cross-section, which increases in amplitude away from the bar centre. The relaxation in the edge-region was also seen in the previous studies on (Ga,Mn)As-based devices 18 19 20 21 . An interesting feature of this profile is the abrupt decrease in amplitude in the regions near to the edges of the bar.…”

“…The lattice mismatch imposes a built-in compressive strain in the magnetic layer, which can be relaxed by etching of the continuous film into patterned devices. The effect of strain-relaxation on magnetic anisotropy was studied extensively in the diluted magnetic semiconductor (Ga,Mn)As 18 19 20 21 . There, the low magnetic moment prevented the formation of regular domain patterns and the observations were interpreted using a single domain model.…”

Growth, strain, and spin-orbit torques in epitaxial Ni-Mn-Sb films sputtered on GaAs

“…Our samples have growth-induced strain that modifies the lattice constant away from the bulk value. Although it is difficult to make a direct quantitative comparison between NiMnSb on different substrates, we can note that the magnitude of H 2 and H 4 observed in our study matches fairly well with that measured by Gerhard et al It is also possible that when epitaxial ferromagnetic films with growth-induced strain are lithographically patterned, uniaxial strain relaxation takes place, leading to a pattern-induced uniaxial magnetic anisotropy [52,53]. We would expect a similar anisotropy term in our NiMnSb film where the growth-induced compressive strain (c/a = 3.5 × 10 −4 ) might relax when patterning a bar.…”

Effect of Rashba Spin-Orbit Coupling on the Spin Polarization of Holes in Two-Dimensional GaMnAs Magnetic Semiconductors

“…Even though not all expectations did materialize so far the interest in such materials is still rather high [2,3]. Recent theoretical works on magnetic semiconductors have been mostly focused on the origin of ferromagnetic ordering [1,2,[4][5][6][7], magnetic anisotropy [8][9][10][11][12], and the effect of strain on the energy spectrum and magnetic anisotropy [13][14][15].…”