Influence of Cr Doping on the Critical Behavior of Amorphous Alloy Ribbons Fe_78–xCr_xSi₄Nb₅B₁₂Cu₁

Though many previous works focused on studying Cr-doped Fe–Si–Nb–B–Cu amorphous alloys, magnetic-interaction mechanismsin these materials have not been carefully investigated yet. Dealing with these issues, we have prepared the amorphous alloy ribbonsFe_78−xCr_x Si₄Nb₅B₁₂Cu₁ with x = 1, 3, and 6, and then studied their magnetic and critical properties. Magnetization versustemperature and magnetic-field measurements, MHT, performed on a vibrating sample magnetometer reveal that the Cr-contentincrease in Fe_78−xCr_xSi₄Nb₅B₁₂Cu₁ reduces the TC from 430 K for x = 1 to about 322 K (for x = 6). This indicates the declineof ferromagnetic (FM) exchange interactions between Fe atoms when there is the presence of Cr atoms. We have also analyzed theM(H) data at the temperatures in the vicinity of the TC using the modified Arrott plot method and the scaling hypothesis, anddetermined the values of the critical exponents β = 0.367–0.376 and γ = 1.315–1.338. These values are close to those expected forthe 3-D Heisenberg model with β = 0.365 and γ = 1.336, proving the existence of short-range FM order in the amorphous alloyribbons.