Correlation of electrical properties with magnetic properties for ferromagnetic (Ga_1-xMn_x)As epilayer

The correlation of electrical properties with magnetic properties for the (Ga_1-xMn_x)As epilayer was investigated. For electrical transport measurements, it was clearly observed that the electrical mobility is increased with decreasing temperatures for both the (Ga_0.974Mn_0.026)As/LT-GaAs epilayer and the LT-GaAs:Be epilayer. However, a different behavior was observed at the cryogenic temperature region. The electrical mobility of (Ga_0.974Mn_0.026)As/LT-GaAs epilayer increases with decreasing temperature, while the mobility of LT-GaAs:Be epilayer decreases with decreasing temperature. In Arrhenius plots of carrier mobility for the (Ga_0.974Mn_0.026)As/LT-GaAs epilayer, the critical point is observed at 69 K, and this value is almost the same as the T_C. This result indicates that the carrier transport in ferromagnetic (Ga_1-xMn_x)As epilayers might be related to a spin-ordering effect because the spins will be arranged with the same direction below the T_C, and this will lead to reducing the probability of spin-disorder scattering. Therefore, the observation of a gradual drop below the T_C in the temperature-dependent resistivity curve is expected to be a result of the spin-ordering effect in the ferromagnetic (Ga_0.974Mn_0.026)As/LT-GaAs epilayer.