Critical behavior of the ferromagnetic-paramagnetic phase transition in Fe90-xNixZr10 alloy ribbons.

This work presents a detailed study on the critical behavior of the ferromagnetic-paramagnetic (FM-PM) phase transition in Fe90_xNixZr10 (x=0 and 5) alloy ribbons. Basing on field dependences of magnetization (M-H), M² versus H/M plots prove the alloys exhibiting a second-order magnetic phase transition. To investigate the nature of the FM-PM phase transition at TC = 245 and 306 K for x= 0 and 5, respectively, we performed a critical-exponent study. The values of critical components β, γ, and δ determined by using the modified Arrott plots, Kouvel-Fisher (KF), and critical isotherm analyses agree with each other. For x = 0, the critical parameters β = 0.365 6 0.013 and γ = 1.615 ± 0.033 are obtained by modified Arrott plots while γ = 0.368 6 0.008 and γ = 1.612 6 0.016 are obtained by the KF method. These values are close to those expected for the 3D-Heisenberg model, revealing short-range FM interactions in Fe90Zr10. Meanwhile, for x=5, the values of the critical parameters β = 0.423 6 0.008 and δ = 1.325 6 0.036 are obtained by modified Arrott plots, and P = 0.425 6 0.006 and γ = 1.323 6 0.012 are obtained by the KF method. The falling of the γ value in between the values of the mean-field theory (β = 0.5) and the 3D-Heisenberg model (β = 0.365) indicates an existence of FM short-range order and magnetic inhomogeneity in Fe85Ni5Zr10. With a partial replacement of Ni for Fe in Fe90_xNixZr10, the value of the critical exponent γ trends to shift towards that of the mean-field theory. Such the result proves the presence of Ni favors establishing FM long-range order. The nature of this phenomenon is carefully discussed. [ABSTRACT FROM AUTHOR]