Novel Germanium-Based Magnetic Semiconductors

Epitaxial synthesis and properties of novel Co and Mn-doped Ge magnetic semiconductors were studied. Epitaxial growth of high quality films with high doping concentrations has been stabilized by the use of two dopants. The magnetic and transport properties of the system exhibit high $T_C$ and large magnetoresistance effects that can be controlled systematically by the doping concentration. The maximum $T_C$ achieved in the semiconducting materials is $\sim 270\mathrm{K}$ at a composition of ${\mathrm{C}\mathrm{o}}_{0.12}{\mathrm{M}\mathrm{n}}_{0.03}{\mathrm{G}\mathrm{e}}_{0.85}$.