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

Abstract

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.

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

“…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.…”

“…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.…”

“…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.…”

Magnetotransport effects in polar versus non-polar SrTiO3based heterostructures

“…Three possible mechanisms for the AMR have been proposed [31]: a. anisotropic Fermi velocities coupled to a finite magnetization through the spin-orbit interaction, b. spin-orbit coupled magnetically polarized carriers with isotropic scattering centers, and c. anisotropic magnetic scattering centers acting on unpolarized spin-orbit coupled carriers. Mechanisms a. and b. usually result in a smaller AMR effect since the magnetization and the spinorbit interaction compete with each other.…”

Non-volatile ferroelectric gating of magnetotransport anisotropy in (Ga,Mn)(As,P)

“…Owing to a strong spin-orbit coupling and a relatively simple band diagram, it quickly became a preferred testing ground for first principle and phenomenological models. [1][2][3] DMS are of particular interest for exploring AMRrelated phenomena because of the possibilities of external control of ferromagnetism, given the carrier-coupled nature of their ferromagnetism and the resulting susceptibility of the magnetic properties to electric field. A variety of manifestations of magneto-electric coupling in (Ga,Mn)As and related materials includes dielectric and ferroelectric gatebased control of ferromagnetic transition, 4,5 coercive field 5,6 and magnetization vector orientation.…”