Roles of Extended and Localized States in the Magnetic and Transport Properties of GaMnAs Alloys

• Published in: Journal of superconductivity and novel magnetism Vol. 26; no. 6; pp. 2201 - 2207
• Main Authors: da Cunha Lima, I. C., de Oliveira, E. J. R., Dias Cabral, E., Boselli, M. A.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Boston Springer US 01-06-2013; Springer
• Subjects: Channels; Characterization and Evaluation of Materials; Condensed Matter Physics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electronic transport in condensed matter; Exact sciences and technology; Fermi level; Fermi surfaces; Gallium arsenide; Gallium arsenides; Impurities; Magnetic Materials; Magnetic properties and materials; Magnetic semiconductors; Magnetism; Manganese; Original Paper; Physics; Physics and Astronomy; Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.); Spin polarized transport; Strongly Correlated Systems; Studies of specific magnetic materials; Superconductivity; Transport; Diluted magnetic semiconductors; Spin-polarized transport; Spintronics; Spin polarized transport; Gallium arsenides; Electrical conductivity; Localized states; Magnetic ordering; Magnetic moments; Spin polarization; Random distribution; Impurities; Fermi level; Manganese arsenides; Impurity bands; Ferromagnetism; Transport processes; Heterostructures
• ISSN: 1557-1939; 1557-1947
• DOI: 10.1007/s10948-012-1433-4

We investigate the spin-polarized transport of holes in GaMnAs/GaAs heterostructures with Mn concentration 5% in which a ferromagnetic order is known to exist. Disorder enters the problem both in the random distribution of Mn centers and impurities, and also in the orientation of the magnetic moments at the Mn sites. We take into account the existence of an impurity band determining the extended or localized nature of the states at and near the Fermi level. Magnetic order and resistivity are inter-related due to the influence of the spin polarization of the impurity band and the effect of the Zeeman splitting on the mobility edge. We obtain two channels of transport, one provided by the extended states above the mobility edge, when this lies below the Fermi level, the other coming out of the thermal excitation of the localized states through a hopping mechanism. We discuss the competition between these two channels in determining, once having obtained the dependence of the resistance on temperature, the metallic or non-metallic nature of the sample.