Spin decoherence of InAs surface electrons by transition metal ions

Spin interactions between a two-dimensional electron system at the InAs surface and transition metal ions, ${\mathrm{Fe}}^{3+}$, ${\mathrm{Co}}^{2+}$, and ${\mathrm{Ni}}^{2+}$, deposited on the InAs surface, are probed by antilocalization measurements. The spin-dependent quantum interference phenomena underlying the quantum transport phenomenon of antilocalization render the technique sensitive to the spin states of the transition metal ions on the surface. The experiments yield data on the magnitude and temperature dependence of the electrons' inelastic scattering rates, spin-orbit scattering rates, and magnetic spin-flip rates as influenced by ${\mathrm{Fe}}^{3+}$, ${\mathrm{Co}}^{2+}$, and ${\mathrm{Ni}}^{2+}$. A high magnetic spin-flip rate is shown to mask the effects of spin-orbit interaction, while the spin-flip rate is shown to scale with the effective magnetic moment of the surface species. The spin-flip rates and their dependence on temperature yield information about the spin states of the transition metal ions at the surface, and in the case of ${\mathrm{Co}}^{2+}$ suggest either a spin transition or formation of a spin-glass system.