Breakdown of the Korringa Law of Nuclear Spin Relaxation in Metallic   GaAs
  We present nuclear spin relaxation measurements in GaAs epilayers using a new pump-probe technique in all-electrical, lateral spin-valve devices. The measured T1 times agree very well with NMR data available for T > 1 K. However, the nuclear spin relaxation rate clearly deviates from the well-established Korringa law expected in metallic samples and follows a sub-linear temperature dependence 1/T1 ~ T^0.6 for 0.1 K < T < 10 K. Further, we investigate nuclear spin inhomogeneities. 
D. K\"olbl, D. M. Zumb\"uhl, A. Fuhrer, G. Salis, S. F. Alvarado
cond-mat.mes-hall cond-mat.dis-nn