Anisotropy of amorphous nanogranular composites CoNbTa-SiO n and CoFeB-SiO n

A comparative investigation of the magnetic properties of amorphous nanogranular composites (Co41Fe39B20) x (SiO n )100 − x and (Co86Nb12Ta2) x (SiO n )100 − x has been performed in the subpercolation region at temperatures in the range 4.2–300 K. The thermomagnetic dependences in the range 4.2–300 K and the processes of magnetization reversal and remanent magnetization relaxation at liquid-helium temperatures have been studied. It has been established that the average anisotropy constants of amorphous nanograins are equal to 3.6–7.0 kJ/m3 for the (Co41Fe39B20) x (SiO n )100 − x composites and 5–8 kJ/m3 for the (Co86Nb12Ta2) x (SiO n )100 − x composites. The fundamental differences in the concentration dependences of the anisotropy constant K eff and the coercive force H C have been revealed for the two systems under investigation. It has been demonstrated that, as the concentration of the metal phase increases, the quantities K eff and H C increase for the (Co86Nb12Ta2) x (SiO n )100 − x composites and decrease for the (Co41Fe39B20) x (SiO n )100 − x composites.