Theory of spin waves in ferromagnetic (Ga,Mn)As

Agnieszka Werpachowska and Tomasz Dietl
Phys. Rev. B 82, 085204 – Published 12 August 2010

Abstract

The collective behavior of spins in a dilute magnetic semiconductor is determined by their mutual interactions and influenced by the underlying crystal structure. Hence, we begin with the atomic quantum-mechanical description of this system using the proposed variational-perturbation calculus and then turn to the emerging macroscopic picture employing phenomenological constants. Within this framework we study spin waves and exchange stiffness in the pd Zener model of (Ga,Mn)As, its thin layers and bulk crystals described by the spds tight-binding approximation. Analyzing the anisotropic part of exchange, we find that the Dzyaloshinskii-Moriya interaction may lead to a cycloidal spin arrangement and uniaxial in-plane anisotropy of diagonal directions in thin layers, resulting in a surfacelike anisotropy in thicker films. We also derive and discuss the spin-wave contribution to magnetization and Curie temperature. Our theory reconstructs the values of stiffness determined from the temperature dependence of magnetization but reproduces only partly those obtained from analyzing precession modes in (Ga,Mn)As thin films.

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  • Received 13 June 2010

DOI:https://doi.org/10.1103/PhysRevB.82.085204

©2010 American Physical Society

Authors & Affiliations

Agnieszka Werpachowska

  • Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, PL-02-668 Warsaw, Poland

Tomasz Dietl

  • Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, PL-02-668 Warsaw, Poland and Institute of Theoretical Physics, University of Warsaw, PL-00-681 Warsaw, Poland

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Vol. 82, Iss. 8 — 15 August 2010

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