Magnetic behavior, transport properties and nanocrystallization of melt-spun Y_xCe_(50 - X)Cu_(42)Al_8 (0 ≤ x ≤ 50) amorphous system

摘要

Amorphous Y_xCe_(50 - x)Cu_(42)Al_8 (0 ≤ x ≤ 50) ribbons prepared by melt-spinning on the Cu wheel were subjected to X-ray diffractometry (XRD), differential scanning calorimetry (DSC) and to the measurements of magnetization and resistivity in the temperature range from 1.7 to 300 K. Effective activation energies, characteristic crystallization temperatures and enthalpies of as-quenched alloys have been determined. Two stages of crystallization have been observed in most samples (except shallow effects in Ce_(50)Cu_(42)Al_8). The activation energies have been calculated from the Kissinger relation to be 247 ± 18 and 570 ± 56 kJ/mol for Y_(25)Ce_(25)Cu _(42)Al_8 and Y_(50)Cu_(42)Al_8, respectively. The absence of the endothermic effect for x = 50, usually associated with a glass transition, below the primary crystallization event, indicates the presence of dispersed polyamorphous packing with a wide range of local glass transitions. The magnetization versus temperature plot for Y _(25)Ce_(25)Cu_(42)Al_8 points to a magnetic ordering at temperatures considerably below 50 K. This observation has been confirmed by the temperature dependence of resistivity, which exhibits a singularity at the same temperature. Moreover, a negative temperature coefficient of resistivity, characteristic of disordered systems, was observed. The electrical resistivity in the Y_(25)Ce_(25)Cu _(42)Al_8 amorphous alloy is governed by the weak localization of electrons.