Magnetic properties of Fe$_{1-x}$Co$_x$Si single crystals at low co impurity concentrations

Magnetostatic properties of FeSi and Fe$_{0,98}$Co$_{0,02}$Si single crystals have been studied. It has been found that the temperature and field dependences of the magnetization of monocrystal FeSi are strongly affected by introduction of a small amount of Co (2 %). A description of the results were provided by a model accounting for the formation of superparamagnetic iron clusters, as well as Fe-Co complexes. It is assumed that Fe-Co complexes form a ferromagnetic phase, which is approximately 0.6% of the Fe$_{0,98}$Co$_{0,02}$Si sample weight