Origin of resistivity peak near the Curie temperature and magnetoresistance in Ga _1-xMn _xas epitaxial layers

We have studied the origin of the resistivity peak which is often observed near the Curie temperature on the resistivity temperature characteristic in Ga _1-xMn _xAs epitaxial layers. It was confirmed that the Curie temperature of this ferromagnetic semiconductor is strongly dependent on the concentration of free carriers (holes). The concentration of free holes was controlled by an additional nonmagnetic acceptor (Be) at a fixed concentration of magnetic atoms (Mn) of Ga _1-xMn _xAs (x = 0.03). We show that the temperature dependences of the resistivity at zero magnetic field and of the magnetoresistance can be successfully described by the magnetoimpurity scattering model proposed by Nagaev [Phys. Rep. 346, 387 (2001)] in both the paramagnetic and the ferromagnetic temperature regions. Quantitative analysis of the experimental data in terms of this model yields the value of the p-d exchange integral J _pd = 0.07 eV nm ³ for Ga _0.97Mn _0.03As.