Conduction-Electron Spin Resonance in Degenerate Indium Sesquioxide

Spin resonance due to degenerate conduction electrons has been observed in ${\mathrm{In}}_2$ ${\mathrm{O}}_3$ crystals grown from flux. The isotropic resonance is characterized by a large, negative $g$ shift ($\delta g\simeq -0.12\mathrm{}$) which is markedly strain-sensitive. As a result the CESR line is inhomogeneously broadened, making any interpretation of the line shape quite ambiguous. The spin-lattice relaxation time $T_1$ appears to be in the range ${10}^{-5\mathrm{}}$-${10}^{-7\mathrm{}}$ sec despite the transport scattering time $\tau \sim {10}^{-14\mathrm{}}$ sec and the 6% $g$ shift. It is suggested that such behavior may be characteristic of single-valley band edges.