Zero-field cooled magnetization of amorphous Fe1-xCxparticles-field dependence of the maximum

Abstract

We measured the zero-field cooled magnetization, M_ZPC of a frozen magnetic liquid with amorphous Fe_1-xC_x particles. MZFC has a maximum at T_p approximately=20 K, which is interpreted as due to blocking of superparamagnetic relaxation in single particles. The maximum shifts towards higher temperatures with increasing measuring field. The shift is explained by the nonlinear field dependence of the magnetization of particles with a size distribution. At temperatures below T_p the magnetic particles have a coercivity and remanence in good agreement with those expected for an ensemble of non-interacting uniaxial particles with a random distribution of easy axes.