Nuclear spin relaxation mediated by Fermi-edge electrons in n-type GaAs
M. Kotur+, R. I. Dzhioev+, K. V. Kavokin+*, V. L. Korenev+, B. R. Namozov+, P. E. Pak+, Yu. G. Kusrayev+
+Ioffe Physico-Technical Institute of the RAS, 194021 St.Petersburg, Russia
*Spin Optics Laboratory, St.Peterburg State University, 198504 St.-Peterburg, Russia
Abstract
A method based on the optical orientation technique was developed
to measure the nuclear-spin lattice relaxation time T1 in semiconductors.
It was applied to bulk n-type GaAs, where T1 was measured after switching
off the optical excitation in magnetic fields from 400 to 1200 G
at low (< 30 K) temperatures. The spin-lattice relaxation of nuclei in
the studied
sample with nD = 9 • 1016 cm-3 was found to be determined by
hyperfine scattering of itinerant electrons (Korringa mechanism) which predicts
invariability of T1 with the change of magnetic field and linear dependence
of the relaxation rate on temperature. This result extends the experimentally
verified applicability of the Korringa relaxation law in degenerate
semiconductors,
previously studied in strong magnetic fields (several Tesla), to the moderate
field range.