Probing dynamics of an electron-spin ensemble via a superconducting   resonator
  We study spin relaxation and diffusion in an electron-spin ensemble of nitrogen impurities in diamond at low temperature (0.25-1.2 K) and polarizing magnetic field (80-300 mT). Measurements exploit mode- and temperature-dependent coupling of hyperfine-split sub-ensembles to the resonator. Temperature-independent spin linewidth and relaxation time suggest that spin diffusion limits spin relaxation. Depolarization of one sub-ensemble by resonant pumping of another indicates fast cross-relaxation compared to spin diffusion, with implications on use of sub-ensembles as independent quantum memories. 
V. Ranjan, G. de Lange, R. Schutjens, T. Debelhoir, J. P. Groen, D.   Szombati, D. J. Thoen, T. M. Klapwijk, R. Hanson, L. D...
cond-mat.mes-hall quant-ph