The superferromagnetic state in the ensemble of oriented Stoner-Wohlfarth particles: a coercivity due to phase stability

It is observed experimentally that the coercive field has an anomalous angular dependence at temperatures above the blocking temperature in physically nonpercolated granular films CoFeB-SiO${}_2$ with anisotropic granules oriented in the same direction. It is shown that the anomaly is determined by the singularity of an angular dependence of the critical field causing the absolute loss of phase stability of the superferromagnetic state of an ensemble of interacting superparamagnetic granules.