Effect of annealing on the depth profile of hole concentration in (Ga,Mn)As

Physical Review B (Impact Factor: 3.66). 03/2005; DOI: 10.1103/PhysRevB.71.205213
Source: arXiv

ABSTRACT The effect of annealing at 250 C on the carrier depth profile, Mn distribution, electrical conductivity, and Curie temperature of (Ga,Mn)As layers with thicknesses > 200 nm, grown by molecular-beam epitaxy at low temperatures, is studied by a variety of analytical methods. The vertical gradient in hole concentration, revealed by electrochemical capacitance-voltage profiling, is shown to play a key role in the understanding of conductivity and magnetization data. The gradient, basically already present in as-grown samples, is strongly influenced by post-growth annealing. From secondary ion mass spectroscopy it can be concluded that, at least in thick layers, the change in carrier depth profile and thus in conductivity is not primarily due to out-diffusion of Mn interstitials during annealing. Two alternative possible models are discussed. Comment: 8 pages, 8 figures, to appear in Phys. Rev. B

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A modeling approach for standing spin-wave resonances based on a finite-difference formulation of the Landau-Lifshitz-Gilbert equation is presented. In contrast to a previous study [Bihler et al., Phys. Rev. B 79, 045205 (2009)], this formalism accounts for elliptical magnetization precession and magnetic properties arbitrarily varying across the layer thickness, including the magnetic anisotropy parameters, the exchange stiffness, the Gilbert damping, and the saturation magnetization. To demonstrate the usefulness of our modeling approach, we experimentally study a set of (Ga,Mn)As samples grown by low-temperature molecular-beam epitaxy by means of electrochemical capacitance-voltage measurements and angle-dependent standing spin-wave resonance spectroscopy. By applying our modeling approach, the angle dependence of the spin-wave resonance data can be reproduced in a simulation with one set of simulation parameters for all external field orientations. We find that the approximately linear gradient in the out-of-plane magnetic anisotropy is related to a linear gradient in the hole concentrations of the samples.
    Physical Review B 03/2013; 87(22). · 3.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We theoretically investigate the interplay between local lattice distortions around the Mn(2+) impurity ion and its magnetization, mediated through spin-orbit coupling of holes. We show that the tetrahedral symmetry around the Mn(2+) ion is spontaneously broken and that local Jahn-Teller distortions coupled with growth strain result in uniaxial magnetic anisotropy. We also account for the experimentally observed in-plane uniaxial magnetic anisotropy rotation due to variation of hole density. According to this model, lack of inversion and top-down symmetries of (Ga, Mn)As layers lead to in-plane biaxial symmetry breaking in the presence of Jahn-Teller distortions.
    Journal of Physics Condensed Matter 04/2013; 25(20):206005. · 2.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present the results of combined density functional and many-body calculations of the electronic and magnetic properties of the defect-free digital ferromagnetic heterostructures obtained by doping GaAs with Cr and Mn. While the local-density approximation +U predicts half-metallicity in these defect-free delta-doped heterostructures, we demonstrate that local many-body correlations captured by dynamical mean-field theory induce within the minority-spin channel nonquasiparticle states just above EF. As a consequence of the existence of these many-body states the half-metallic gap is closed and the carriers’ spin polarization is significantly reduced. Below the Fermi level the minority-spin highest valence states are found to localize more on the GaAs layers, being independent of the type of electronic correlations considered. Thus, our results confirm the confinement of carriers in these delta-doped heterostructures, having a spin polarization that follows a different temperature dependence than the magnetization. We suggest that polarized hot-electron photoluminescence experiments might uncover evidence for the existence of many-body states within the minority-spin channel and elucidate their finite-temperature behavior.
    Physical review. B, Condensed matter 01/2011; 83(12). · 3.77 Impact Factor

Full-text (2 Sources)

Available from
May 22, 2014