Muonium formation and magnetic relaxation in dextran and iron-dextran

Zero- and longitudinal field muon spin relaxation was used to study muonium formation in dextran and an iron-dextran complex. The temperature dependen ce of the reduced hyperfine coupling constant, A', was determined for both samples. In addition, superparamagnetic relaxation processes associated wit h the iron-dextran cares were characterized. The resulting zero-held muon s pin relaxation is found to be stretched exponential in farm, indicating a b road distribution of correlation times for the internal magnetic fields, wh ilst the temperature dependence of the muon relaxation rate provides eviden ce that the superparamagnetic relaxation follows a thermally activated Arrh enius behaviour with a characteristic activation energy E-a/k = 84 K. Copyr ight (C) 2000 John Wiley & Sons, Ltd.