Muon spin relaxation study of spin dynamics in a polysaccharide iron complex

Polysaccharide iron complex, a ferritin analog, has been examined with zero -field muon spin-relaxation at temperatures from 2 to 40 K. Spectra exhibit a clear separation of static moments and collective excitations at low tem peratures. At intermediate temperatures, superparamagnetic relaxation is ob served and a blocking temperature of T-B = 10 +/-2.5 K is measured, in agre ement with transmission Mossbauer spectra and frequency dependent chi (ac) data. Superparamagnetic relaxation rates of 20-150 MHz are in agreement wit h those extrapolated from Mossbauer spectra using a multilevel magnetic rel axation model. (C) 2001 American Institute of Physics.