The origin and control of the sources of AMR in (Ga,Mn)As devices

Rushforth, A. W.; Výborný, Karel; King, C. S.; Edmonds, K. W.; Campion, R. P.; Foxon, C. T.; Wunderlich, J.; Irvine, A. C.; Novák, V.; Olejník, K.; Kovalev, Alexey A.; Sinova, Jairo; Jungwirth, T.; Gallagher, B. L.

doi:10.1016/j.jmmm.2008.04.070

Cited by 20 publications

(18 citation statements)

References 25 publications

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“…On the other hand, electromagnetic scatterers ϰ 3 2 1 + j x,y produce negative AMR in the Kohn-Luttinger model 37,38 in the very same way as it is shown in Fig. 6͑b͒ for the Dresselhaus model, and in both cases, this behavior can again be inferred using relations ͑7͒ and ͑5͒ with j x,y and x,y replaced by 3 2 1 + j x,y and 1 + x,y , respectively.…”

Section: Amr In the Spherical Kohn-luttinger Modelsupporting

confidence: 64%

“…Analysis of these effects relates our work to previous theoretical studies of the AMR in ͑Ga, Mn͒As diluted magnetic semiconductors. 29,31,37,38 The validity of the heuristic analysis of the AMR is confirmed in Sec. III where we explain the relation between the RTA and the exact solution to the integral Boltzmann equation.…”

Section: Introductionmentioning

confidence: 64%

“…Contrary to the Dresselhaus model ͑4͒, the SOI of the Kohn-Luttinger model ͑6͒ in combination with polarized scatterers therefore can produce AMR of either sign, e.g., depending on the carrier-density-controlled screening of the impurities. 37,38 This qualitative difference between Dresselhaus and Kohn-Luttinger models highlights the fact that knowledge of spin textures, such as Figs. 2͑a͒ or 4͑a͒, may not be sufficient to analyze the scattering properties of the model and appropriate matrix elements such as Eqs.…”

Section: Amr In the Spherical Kohn-luttinger Modelmentioning

confidence: 99%

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Anisotropic magnetoresistance of spin-orbit coupled carriers scattered from polarized magnetic impurities

et al. 2009

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Anisotropic magnetoresistance ͑AMR͒ is a relativistic magnetotransport phenomenon arising from combined effects of spin-orbit coupling and broken symmetry of a ferromagnetically ordered state of the system. In this work we focus on one realization of the AMR in which spin-orbit coupling enters via specific spin-textures on the carrier Fermi surfaces and ferromagnetism via elastic scattering of carriers from polarized magnetic impurities. We report detailed heuristic examination, using model spin-orbit coupled systems, of the emergence of positive AMR ͑maximum resistivity for magnetization along current͒, negative AMR ͑minimum resistivity for magnetization along current͒, and of the crystalline AMR ͑resistivity depends on the absolute orientation of the magnetization and current vectors with respect to the crystal axes͒ components. We emphasize potential qualitative differences between pure magnetic and combined electromagnetic impurity potentials, between short-range and long-range impurities, and between spin-1/2 and higher spin-state carriers. Conclusions based on our heuristic analysis are supported by exact solutions to the integral form of the Boltzmann transport equation in archetypical two-dimensional electron systems with Rashba and Dresselhaus spin-orbit interactions and in the three-dimensional spherical Kohn-Littinger model. We include comments on the relation of our microscopic calculations to standard phenomenology of the full angular dependence of the AMR, and on the relevance of our study to realistic, two-dimensional conduction-band carrier systems and to anisotropic transport in the valence band of diluted magnetic semiconductors.

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Section: Amr In the Spherical Kohn-luttinger Modelsupporting

confidence: 64%

Section: Introductionmentioning

confidence: 64%

Section: Amr In the Spherical Kohn-luttinger Modelmentioning

confidence: 99%

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Anisotropic magnetoresistance of spin-orbit coupled carriers scattered from polarized magnetic impurities

et al. 2009

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“…The virtual-crystal k · p approximation for hole states and mean-field treatment of their exchange interaction with Mn d-shell moments allow for efficient numerical simulations. [1][2][3][4] The approach has proved useful in researching many thermodynamic and magnetotransport properties of ͑Ga,Mn͒As samples with metallic conductivities, 3 such as the measured transition temperatures, 5-8 the anomalous Hall effect, [9][10][11][12] anisotropic magnetoresistance, 9,[11][12][13][14][15][16] spin-stiffness, 17 ferromagnetic domain-wall widths, 18,19 Gilbert damping coefficient, [20][21][22] and magneto-optical coefficients. 1,12,20,23,24 In this study we systematically explore the reliability of the effective model in predicting the magnetocrystalline anisotropies of ͑Ga,Mn͒As epilayer and microdevices.…”

Section: Introductionmentioning

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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“…We suggest that the AMR coefficient changes sign as transport goes from metallic to hopping 13,15 , leading to the observed magnetoresistance. This claim is supported by angle-dependent magnetoresistance measurements at a field of 300 mT, strong enough to (nearly) align the magnetization to the external field.…”

Section: Read-out Of the Informationmentioning

confidence: 83%

Novel spintronic devices using local anisotropy engineering in (Ga,Mn)As

2008

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Ga,Mn)As is the prototypical ferromagnetic semiconductor for spintronics devices, largely because of its rich magnetic and transport anisotropy. Until recently, the lack of local anisotropy control limited device design as all elements inherited the anisotropy of the parent layer. We report here on anisotropy control through lithographically engineered strain relaxation. By patterning the layer, we allow local and strain relaxation and controlled deformation of the crystal. Because of the strong spin orbit coupling, this leads to a new anisotropy term that can be tuned independently for each element of a compound device. We use this method to demonstrate a novel non-volatile memory element.

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The origin and control of the sources of AMR in (Ga,Mn)As devices

Cited by 20 publications

References 25 publications

Anisotropic magnetoresistance of spin-orbit coupled carriers scattered from polarized magnetic impurities

Anisotropic magnetoresistance of spin-orbit coupled carriers scattered from polarized magnetic impurities

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

Novel spintronic devices using local anisotropy engineering in (Ga,Mn)As

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