2005/03/16 by Gregory A. Fiete, Gergely Zaránd, Gergely Zarand +3
Materials Science · Physics and Astronomy · #Magnetic and transport properties of perovskites and related materials #Physics of Superconductivity and Magnetism #ZnO doping and properties #cond-mat.dis-nn #cond-mat.mtrl-sci
paper · pdf · doi:10.1103/physrevb.72.045212
published as Phys. Rev. B 72, 045212 (2005) · 15 pages, 12 figures
arxiv created 2005/03/16 · openalex publication_date 2005/07/18 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We derive an effective Hamiltonian for Ga_1\ensuremath-xMnxAs in the dilute limit, where Ga_1\ensuremath-xMnxAs can be described in terms of spin F=3∕2 holes hopping between the Mn sites and coupled to the local Mn spins. We determine the parameters of our model from microscopic calculations using both a variational method and an exact diagonalization within the so-called spherical approximation. Our approach treats the extremely large Coulomb interaction in a nonperturbative way and captures the effects of strong spin-orbit coupling and Mn positional disorder. We study the effective Hamiltonian in a mean-field and variational calculation, including the effects of interactions between the holes at both zero and finite temperature. We study the resulting magnetic properties, such as the magnetization and spin-disorder manifest in the generically noncollinear magnetic state. We find a well-formed impurity band fairly well separated from the valence band up to xactive\ensuremath\lesssim0.015 for which finite-size scaling studies of the participation ratios indicate a localization transition, even in the presence of strong on-site interactions, where xactive<xnom is the fraction of magnetically active Mn. We study the localization transition as a function of hole concentration, Mn positional disorder, and interaction strength between the holes.