AbstractsPhysics

This thesis investigates the magnetotransport properties of ultrathin (Ga,Mn)Sb layers in a field-effect structure. We fabricate a metal-insulator-semiconductor field-effect structure with a thin (Ga,Mn)Sb channel and investigate its magnetotransport properties, as functions of temperature, external magnetic field, and gate electric field. The results show that one can control magnetic properties of (Ga,Mn)Sb by applying electric fields, as similar to (Ga,Mn)As. The most prominent finding is that the Curie temperature of (Ga,Mn)Sb can be modulated by gating but in somewhat different manner from (Ga,Mn)As. For (Ga,Mn)Sb, we determine experimentally the relationship between the Curie temperature TC and hole concentration p, to be Tc â p^Ï with Ï of 1.3~1.6, which is several times larger than Ï ~ 0.2 reported previously for (Ga,Mn)As. We show that the value of Ï can be reproduced by the numerical calculations based on the adapted p-d Zener model with non-uniform hole distribution, and the calculation indicates the accumulation of holes in (Ga,Mn)Sb in the vicinity of the interface with a gate insulator, while for (Ga,Mn)As the depletion of holes at the interface. The results are consistent with the reported Fermi energy pinning positions for p-GaSb and p-GaAs. We also find that the conductivity dependence of the Hall conductivity is different from that reported for (Ga,Mn)As. The findings are of great importance for employing thin and ultrathin layers of (Ga,Mn)Sb or related compounds in the concept of spintronics devices, where magnetic and electronic properties are mutually controlled.