Initial magnetization analysis of iron cluster assemblies

Abstract

Nearly monodispersed oxide-coated Fe cluster assemblies were prepared using a plasma-gas-condensation style cluster beam deposition apparatus (D. L. Peng et al. J. Appl. Phys. 92 3075 (2002)). The characterization of such assemblies is presented using SQUID magnetometry. The aim of this contribution is the interpretation of the initial magnetization curves instead of the usual presentation of hysteresis loops and coercivities. The description of the initial magnetization is based on a proposed vector model valid for Stoner-Wohlfarth particles. The model includes the particles' anisotropy and possible interactions regarding these influences as equivalent magnetic fields. The model is an extension of the one described by Michele et al. (J. Phys.: Condens. Matter 16 427 (2004)) regarding the fact that in a completely demagnetized state, in the sample consisting of a very large number of particles always equal anisotropy fields of opposite signs are present. We measured the initial magnetization curves for different temperatures and present the temperature dependence of the model's parameters. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.