ZERO-FIELD COOLED MAGNETIZATION OF AMORPHOUS FE1-XCX PARTICLES-FIELD DEPENDENCE OF THE MAXIMUM

We measured the zero-field cooled magnetization, M(ZFC). Of a frozen magnetic liquid with amorphous Fe1-xCx particles. M(ZFC) has a maximum at T-p approximate to 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.