부산대학교 도서관

In this work, we have presented a detailed study on the critical behavior at a magnetic field below 10 kOe of the ferromagnetic-paramagnetic (FM-PM) phase transition in amorphous FeNiZr ribbons with x= 0-15, which were prepared by a rapid-quenching method. The results revealed that all the samples undergo a second-order phase transition. The Curie temperature ( T ) depends strongly on Ni concentration ( x), which increases from 245 K (for x= 0) up to 403 K (for x= 15). Based on isothermal magnetization data, M( H), the values of the critical exponents β, γ, and δ around the FM-PM phase transition were determined by using the modified Arrott plots, the Kouvel-Fisher methods, and the critical isotherm analyses. In the case of low Ni concentrations ( x= 0 and 5), the β value is close to that expected for the 3D Heisenberg model revealing an existence of short-range FM interactions in these ribbons. In contrast, the falling of the β values in between the values of mean-field theory and the 3D Heisenberg model for high Ni concentration ( x= 10 and 15) indicates a coexistence of short- and long-range FM interactions. It means that the presence of Ni favors establishing FM long-range order. [ABSTRACT FROM AUTHOR]