Spin-dependent transport in heavily Mn-doped GaAs

Abstract

The theory of magnetotransport in heavily Mn-doped GaAs, a p-type ferromagnetic semiconductor, is developed in the weak coupling limit by calculating the temperature and magnetic field dependences of the spin disorder scattering-limited hole mobility. The theory is based on the exchange interaction between the itinerant holes and the localized 3d spins of the Mn ions, and it is developed by using Zubarev's double-time Green's functions. The relaxation time of the charge carriers is calculated from the imaginary part of the self-energy appearing in the derived hole propagator. Adding a contribution from impurity scattering the total hole mobility is estimated. Comparison to the experimental resistivity data shows that a good agreement with the measured results is obtained only if the short-range order and the consequent T dependence of the critical scattering are taken into account in the paramagnetic region. The measured resistivity peak near Curie temperature is broader than the calculated one, which together with the estimated large exchange parameter Jpd = 2.3 eV calls for an extension of the present theory to the intermediate or strong coupling cases.