Pressure Dependent Magnetotransport Properties of Dilute Magnetic Semiconductors

The Mn$^{2+}$ ions in (III,Mn)V ferromagnetic semiconductors provide magnetic moment and at the same time they act as a source of valence-band holes that mediate the Mn$^{2+}$-Mn$^{2+}$ interactions. This coupling results in the ferromagnetic phase. By using hydrostatic pressure to continuously tune the wavefunction overlap, one can control the strength of the ferromagnetic coupling resulting in a spectacular enhancement of the magnetization and the Curie-temperature [M. Csontos et al. Nature Materials \textbf{4}, 447 (2005)]. Magnetoresistance measurements on the magnetic semiconductor (In,Mn)Sb suggest that magnetic scattering in this material is dominated by isolated Mn$^{2+}$ ions located outside the ferromagnetically ordered regions [M. Csontos et al. Phys. Rev. Lett. \textbf{95}, 227203 (2005)]. The transport properties in presence of high magnetic field and hydrostatic pressure have also been investigated by Hall-effect and thermoelectric power measurements.