Boltzmann theory of engineered anisotropic magnetoresistance in (Ga,Mn)As

Jungwirth, T.; Abolfath, M.; Sinova, Jairo; Kučera, Jaroslav; MacDonald, Allan H.

doi:10.1063/1.1523160

Cited by 83 publications

(133 citation statements)

References 19 publications

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“…Longrange tails of the impurity potentials, which become less important with increasing level of doping, are neglected. ͑Note, that the Thomas-Fermi screening length is only 3 -5 Å for typical carrier densities, 49 i.e., comparable to the lattice constant.͒ Also lattice relaxation effects are neglected within the CPA.…”

Section: Discreteness Of Random Mn Ga Positions Superexchangementioning

confidence: 99%

Prospects for high temperature ferromagnetism in (Ga,Mn)As semiconductors

et al. 2005

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We report on a comprehensive combined experimental and theoretical study of Curie temperature trends in ͑Ga,Mn͒As ferromagnetic semiconductors. Broad agreement between theoretical expectations and measured data allows us to conclude that T c in high-quality metallic samples increases linearly with the number of uncompensated local moments on Mn Ga acceptors, with no sign of saturation. Room temperature ferromagnetism is expected for a 10% concentration of these local moments. Our magnetotransport and magnetization data are consistent with the picture in which Mn impurities incorporated during growth at interstitial Mn I positions act as double-donors and compensate neighboring Mn Ga local moments because of strong nearneighbor Mn Ga u Mn I antiferromagnetic coupling. These defects can be efficiently removed by post-growth annealing. Our analysis suggests that there is no fundamental obstacle to substitutional Mn Ga doping in high-quality materials beyond our current maximum level of 6.8%, although this achievement will require further advances in growth condition control. Modest charge compensation does not limit the maximum Curie temperature possible in ferromagnetic semiconductors based on ͑Ga,Mn͒As.

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Section: Discreteness Of Random Mn Ga Positions Superexchangementioning

confidence: 99%

Prospects for high temperature ferromagnetism in (Ga,Mn)As semiconductors

et al. 2005

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“…Such incoherent sum, with appropriately defined scattering operators, was used earlier 21 to describe more realistic ͑Ga,Mn͒As systems that contain interstitial Mn atoms or As antisites in addition to the substitutional Mn. To summarize our model description of substitutional Mn impurities in GaAs, the Mn atoms in Ga 1−x Mn x As enter our model at three different places: ͑i͒ As acceptors and in the absence of other dopants they determine the Fermi level E F and therefore the density of states and Fermi velocities.…”

Section: B Scattering On Random Mn Impuritiesmentioning

confidence: 99%

“…where 1 denotes a 6 ϫ 6 unity matrix, is the host semiconductor dielectric constant, q TF = ͱ e 2 g / the Thomas-Fermi screening wavevector, 21,32 and g the density of states at the Fermi level.…”

Section: B Scattering On Random Mn Impuritiesmentioning

confidence: 99%

“…IV include analytically evaluated anisotropic conductivity on several levels of model complexity, and the most simplified model allows to clearly identify the physical mechanism that determines the sign of the AMR in ͑Ga,Mn͒As. Our approach 21 is based on the relaxation-time approximation ͑RTA͒ and it would be desirable to put the present results into more precise terms by exactly solving the Boltzmann equation in its full integral form as the authors did for the simpler Rashba system recently. 11,22 Although this solution is presently not available, we explain in a short discussion at the end of Sec.…”

Section: Introductionmentioning

confidence: 99%

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Microscopic mechanism of the noncrystalline anisotropic magnetoresistance in (Ga,Mn)As

et al. 2009

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Starting with a microscopic model based on the Kohn-Luttinger Hamiltonian and kinetic p-d exchange combined with Boltzmann formula for conductivity we identify the scattering from magnetic Mn combined with the strong spin-orbit interaction of the GaAs valence band as the dominant mechanism of the anisotropic magnetoresistance ͑AMR͒ in ͑Ga,Mn͒As. This fact allows to construct a simple analytical model of the AMR consisting of two heavy-hole bands whose charge carriers are scattered on the impurity potential of the Mn atoms. The model predicts the correct sign of the AMR ͑resistivity parallel to magnetization is smaller than perpendicular to magnetization͒ and identifies its origin arising from the destructive interference between electric and magnetic part of the scattering potential of magnetic ionized Mn acceptors when the carriers move parallel to the magnetization.

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“…Microscopic numerical simulations [6,12] consistently describe the sign and magnitudes of the non-crystalline AMR and capture the more subtle crystalline terms associated with e.g. growth-induced strain [8,12].…”

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Anisotropic Magnetoresistance Components in (Ga,Mn)As

et al. 2007

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Our experimental and theoretical study of the non-crystalline and crystalline components of the anisotropic magnetoresistance (AMR) in (Ga,Mn)As is aimed at exploring basic physical aspects of this relativistic transport effect. The non-crystalline AMR reflects anisotropic lifetimes of the holes due to polarized Mn impurities while the crystalline AMR is associated with valence band warping. We find that the sign of the non-crystalline AMR is determined by the form of spin-orbit coupling in the host band and by the relative strengths of the non-magnetic and magnetic contributions to the impurity potential. We develop experimental methods directly yielding the non-crystalline and crystalline AMR components which are then independently analyzed. We report the observation of an AMR dominated by a large uniaxial crystalline component and show that AMR can be modified by local strain relaxation. We discuss generic implications of our experimental and theoretical findings including predictions for non-crystalline AMR sign reversals in dilute moment systems. Anisotropic magnetoresistance (AMR) is a response of carriers in magnetic materials to changes of the magnetization orientation. Despite its importance in magnetic recording technologies the understanding of the microscopic physics of this spin-orbit (SO) coupling induced effect is relatively poor. Phenomenologically, AMR has a non-crystalline component, arising from the lower symmetry for a specific current direction, and crystalline components arising from the crystal symmetries [1,2]. In ferromagnetic metals, values for these coefficients can be obtained by numerical ab initio transport calculations [3], but these have no clear connection to the standard physical model of transport arising from spin dependent scattering of current carrying low mass s-states into heavymass d-states [4]. Experimentally, the non-crystalline and, the typically much weaker, crystalline AMR components in metals have been indirectly extracted from fitting the total AMR angular dependences [2].Among the remarkable AMR features of (Ga,Mn)As ferromagnetic semiconductors are the opposite sign of the non-crystalline component (compared to most metal ferromagnets) and the crystalline terms reflecting the rich magnetocrystalline anisotropies [5,6,7,8,9,10,11]. Microscopic numerical simulations [6,12] consistently describe the sign and magnitudes of the non-crystalline AMR and capture the more subtle crystalline terms associated with e.g. growth-induced strain [8,12]. As in metals, however, the basic microscopic physics of the AMR still needs to be elucidated which is the aim of the work presented here.Theoretically, we separate the non-crystalline and crystalline components by turning off and on band warping and match numerical microscopic simulations with model analytical results. This provides the physical interpretation of the origin of AMR, and of the sign of the noncrystalline term in particular. Experimentally, we obtain direct and independent access to the non-crystalline and crystalli...

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Boltzmann theory of engineered anisotropic magnetoresistance in (Ga,Mn)As

Cited by 83 publications

References 19 publications

Prospects for high temperature ferromagnetism in (Ga,Mn)As semiconductors

Prospects for high temperature ferromagnetism in (Ga,Mn)As semiconductors

Microscopic mechanism of the noncrystalline anisotropic magnetoresistance in (Ga,Mn)As

Anisotropic Magnetoresistance Components in (Ga,Mn)As

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