Effect of annealing on specific magnetization of Fe-Cr-Nb-Cu-Si-B with the partial replacement of Fe by chromium

The samples Fe_73.5-xCr_xNb₃Cu₁Si_13.5B₉ [x = 7, 9, 10 and 12.5 are prepared in the amorphous state in the form of thin ribbons by rapid quenching technique at wheel speed of 25 m s⁻¹ in an Ar atmosphere. The composition was sintered at the temperature 450–8000 C for half an hour. The saturation magnetization (Ms) and Curie temperature (Tc) of these alloys decrease linearly with the increase of Cr content for the entire composition range due to dilution of Fe magnetic moment and weakening of exchange interaction between of magnetic atoms. The critical composition for disappearance of ferromagnetism fall of curve Ms with the replacement Fe by Cr, where the nearest neighbor coupling is longer dominant and intermediate range occur, giving rise to a significant portion of antiferromagnetic interaction. The Curie temperature decreases due the weaker interaction among the Fe magnetic moment. The structural relaxation is associated with the magnetization up to the annealed temperature 600 °C and the chemical disorderness arise with reference to enhancement of M of annealed samples. M versus H curves sharply rise which indicates the formation of crystallization and it seems to ferromagnetic and for x = 12.5 which is paramagnetic in the amorphous condition with Tc = 246 K. This increase of M for the four samples are due to the evolution of ferromagnetic α-Fe (Si) nanograin crystal.