Magnetic properties of Cr2O3 nanoparticles

Magnetization measurements of similar to150Angstrom size Cr2O3 particles prepared by chemical precipitation are reported. Zero-field-cooled (ZFC) susceptibility exhibits a peak characterizing a blocking behaviour at T-B approximate to 40 K. Above the bifurcation point of similar to160 K the reversal magnetizations vary linearly with H, whereas below it both ZFC and field-cooled hysteresis loops exhibit large coercivities. Exchange fields of similar to2000 Oe are also observed at low temperatures. Magnetization relaxes according to the equation M(t) = M(t(0))[1 - S(T)ln((t + t(0))/tau(0))]. Magnetic viscosity S(T) is found to be linear for T less than or equal to 10 K. (C) 2003 Published by Elsevier B.V.