An extensive comparison of anisotropies in MBE grown (Ga,Mn)As material

Gould, C.; Mark, S.; Pappert, K.; Dengel, Radu-Gabriel; Wenisch, J.; Campion, R. P.; Rushforth, A. W.; Chiba, Daichi; Li, Z; Liu, X; Roy, W. Van; Ohno, Hideo; Furdyna, J. K.; Gallagher, B. L.; Βrunner, Karl; Schmidt, G.; Molenkamp, L. W.

doi:10.1088/1367-2630/10/5/055007

Cited by 27 publications

(29 citation statements)

References 16 publications

(20 reference statements)

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“…͑A weak uniaxial component along the main crystal axes ͓͑100͔/͓010͔͒ has also been detected. 45,46 ͒ The theoretical model used so far to describe the easy-axis reorientation between the in-plane and out-of-plane alignment, assuming the growth strain, can account only for the cubic in-plane anisotropy component. In this case we find two easy axes perpendicular to each other either along the main crystal axes or along the diagonals, depending on the Mn concentration and hole density, as shown in Fig.…”

Section: B In-plane Anisotropy: Competition Of Cubic and Uniaxial Comentioning

confidence: 99%

Magnetocrystalline anisotropies in (Ga,Mn)As: Systematic theoretical study and comparison with experiment

et al. 2009

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We present a theoretical survey of magnetocrystalline anisotropies in ͑Ga,Mn͒As epilayers and compare the calculations to available experimental data. Our model is based on an envelope function description of the valence-band holes and a spin representation for their kinetic-exchange interaction with localized electrons on Mn 2+ ions, treated in the mean-field approximation. For epilayers with growth-induced lattice-matching strains we study in-plane to out-of-plane easy-axis reorientations as a function of Mn local-moment concentration, hole concentration, and temperature. Next we focus on the competition of in-plane cubic and uniaxial anisotropies. We add an in-plane shear strain to the effective Hamiltonian in order to capture measured data in bare unpatterned epilayers, and we provide microscopic justification for this approach. The model is then extended by an in-plane uniaxial strain and used to directly describe experiments with strains controlled by post-growth lithography or attaching a piezostressor. The calculated easy-axis directions and anisotropy fields are in semiquantitative agreement with experiment in a wide parameter range.

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Section: B In-plane Anisotropy: Competition Of Cubic and Uniaxial Comentioning

confidence: 99%

Magnetocrystalline anisotropies in (Ga,Mn)As: Systematic theoretical study and comparison with experiment

et al. 2009

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“…␦ / 2 is determined by the angle difference between the corners of the rectangle defined by the first switching fields ͑green circles͒ close to the ͓100͔ and ͓010͔ directions. 18 These corner points are also the directions where first and second switching fields coincide. We obtain ␦ / 2=͑15Ϯ 2͒°, indicating that the global easy axes are located ͑60Ϯ 2͒°from the ͓110͔ direction and ͑30Ϯ 2͒°from the ͓110͔ direction, respectively.…”

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confidence: 91%

Complex domain-wall dynamics in compressively strainedGa1−xMnxAsepilayers

et al. 2008

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The domain-wall-induced reversal dynamics in compressively strained Ga 1−x Mn x As was studied employing the magneto-optical Kerr effect and Kerr microscopy. Due to the influence of a uniaxial part in the in-plane magnetic anisotropy 90°Ϯ ␦ domain walls with considerably different dynamic behavior are observed. While the 90°+ ␦ reversal is identified to be propagation dominated with a small number of domains, the case of 90°−␦ reversal involves a larger number of nucleation centers. The domain-wall nucleation/propagation energies ⑀ for both transitions are estimated using model calculations from which we conclude that single domain devices can be achievable using the 90°+ ␦ mode.The discovery of the ferromagnetic semiconductor Ga 1−x Mn x As and the possible implementation into spintronic devices triggered great interest in understanding its fundamental properties. 1 The linkage between carrier density and magnetic properties in this hole-mediated ferromagnet allows tuning of its magnetic properties such as the Curie temperature ͑T c ͒ upon changing the carrier concentration. 2,3 In addition, magnetic domain-wall ͑DW͒ logic operations may be implemented 4 including magnetoresistive read-outs. However, any application in this direction requires full control over magnetic reversal dynamics, which in most cases happens via the nucleation and propagation of domain walls.A good understanding of the magnetic anisotropy landscape is also required not only for the design of magnetoresistive devices but also because magnetic anisotropy can manifest in the domain-wall dynamics. The magnitude of the magnetic anisotropy is related to important parameters such as the domain-wall energy and width, 5 which can determine a process to be propagation or nucleation dominated. This can be very well visualized in the effect of a nonuniform anisotropy distribution in simulated reverse domain patterns. 6 So far, domain-wall studies by means of Kerr microscopy ͑KM͒ in Ga 1−x Mn x As have been mostly performed in films with tensile strain where the magnetization pointed perpendicular to the plane. 7 Ga 1−x Mn x As with in-plane magnetization has been extensively studied using magnetotransport measurements. 8,9 However, this technique does not provide spatially resolved information about DW nucleation and propagation processes. In this study we present the direct observation of DW motion in compressively strained Ga 1−x Mn x As by KM and the dependence of the DW dynamics on the direction of the applied magnetic field. While an earlier magneto-optical study in the literature 10 did not address possible anisotropies in the DW dynamics, our KM results reveal a distinct anisotropy in the DW dynamics dependent on the direction of the applied magnetic field with respect to the crystal axes. From the analysis of angleresolved magneto-optical Kerr effect ͑MOKE͒ measurements, we attribute this anisotropy to the existence of two different types of DWs. All measurements were done on Hall bar devices of 150 m width, patterned in ͓110͔ and ͓110͔ direc...

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“…It has been demonstrated that a number of pertinent properties of this material can be explained by the p-d Zener model. [3][4][5][6] Magnetic anisotropy of strained ͑Ga,Mn͒As layers can be calculated within this theory and many experimental studies [7][8][9][10][11][12][13][14][15] were devoted to verify its predictions. However, despite these intense studies, some important features of magnetic anisotropy in this system are at present not completely understood.…”

Section: Introductionmentioning

confidence: 99%

Magnetic anisotropy of epitaxial (Ga,Mn)As on(113)AGaAs

et al. 2010

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The temperature dependence of magnetic anisotropy in ͑113͒A ͑Ga,Mn͒As layers grown by molecular-beam epitaxy is studied by means of superconducting quantum interference device magnetometry as well as by ferromagnetic resonance ͑FMR͒ and magnetooptical effects. Experimental results are described considering cubic and two kinds of uniaxial magnetic anisotropy. The magnitude of cubic and uniaxial anisotropy constants is found to be proportional to the fourth and second power of saturation magnetization, respectively. Similarly to the case of ͑001͒ samples, the spin reorientation transition from uniaxial anisotropy with the easy axis along the ͓110͔ direction at high temperatures to the biaxial ͗100͘ anisotropy at low temperatures is observed around 25 K. The determined values of the anisotropy constants have been confirmed by FMR studies. As evidenced by investigations of the polar magnetooptical Kerr effect, the particular combination of magnetic anisotropies allows the out-of-plane component of magnetization to be reversed by an in-plane magnetic field. Theoretical calculations within the p-d Zener model explain the magnitude of the out-of-plane uniaxial anisotropy constant caused by epitaxial strain but do not explain satisfactorily the cubic anisotropy constant. At the same time the findings point to the presence of an additional uniaxial anisotropy of unknown origin. Similarly to the case of ͑001͒ films, this additional anisotropy can be explained by assuming the existence of a shear strain. However, in contrast to the ͑001͒ samples, this additional strain has an out of the ͑001͒ plane character.

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An extensive comparison of anisotropies in MBE grown (Ga,Mn)As material

Cited by 27 publications

References 16 publications

Magnetocrystalline anisotropies in (Ga,Mn)As: Systematic theoretical study and comparison with experiment

Magnetocrystalline anisotropies in (Ga,Mn)As: Systematic theoretical study and comparison with experiment

Complex domain-wall dynamics in compressively strainedGa1−xMnxAsepilayers

Magnetic anisotropy of epitaxial (Ga,Mn)As on(113)AGaAs

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