Influence of Cr Doping on the Critical Behavior of Amorphous Alloy Ribbons Fe78–xCrxSi4Nb5B12Cu1

Though many previous works focused on studying Cr-doped Fe-Si-Nb-B-Cu amorphous alloys, magnetic-interaction mechanisms in these materials have not been carefully investigated yet. Dealing with these issues, we have prepared the amorphous alloy ribbons Fe_78-xCr_xSi₄Nb₅B₁₂Cu₁ with x= 1, 3, and 6, and then studied their magnetic and critical properties. Magnetization versus temperature and magnetic-field measurements, MHT, performed on a vibrating sample magnetometer reveal that the Cr-content increase in Fe_78-xCr_xSi₄Nb₅B₁₂Cu₁ reduces the T_C from 430 K for x= 1 to about 322 K (for x= 6). This indicates the decline of ferromagnetic (FM) exchange interactions between Fe atoms when there is the presence of Cr atoms. We have also analyzed the M(H) data at the temperatures in the vicinity of the T_C using the modified Arrott plot method and the scaling hypothesis, and determined the values of the critical exponents β = 0.367-0.376 and γ = 1.315-1.338. These values are close to those expected for the 3-D Heisenberg model with β = 0.365 and γ = 1.336, proving the existence of short-range FM order in the amorphous alloy ribbons.