Calorimetric investigation of the low temperature specific heat of the amorphous RE-Cu-Y metallic glasses

Abstract

The specific heat, Cp of the RE0.40Cu0·37Y0.23 (RE = Gd, Tb, Dy, Ho, Er, and Lu) metallic glasses have been measured from liquid helium to liquid nitrogen temperatures using the traditional pulse and continuous heating techniques. The average values of the electronic and lattice specific heat coefficients, γ and β were estimated to be of order of 2.35 mJ/mol,K2, and 0.62 mJ/mol,K4 respectively. The corresponding average Debye temperature, θD(0) was estimated to be 145 K. The magnetic contributions to the specific heat, Cm are quite apparent in all samples. Cm has been separated from the nonmagnetic terms with an acceptable accuracy method; by subtracting the nonmagnetic specific heat, of the amorphous Lu0.40Cu0·37Y0.23 sample, which has been prepared with Lu rather than RE. The magnetic phase transition in these magnetic amorphous has been confirmed by the ac susceptibility results, which exhibits quite sharp maximum at the freezing temperature Tf, the spin glass freezing temperature. The magnetic specific heats were characterized by the quite broad maximum at temperature Tm and by the low-temperature linear term in Cm. Values of Tm are higher than Tf values for most of the samples. The magnetic entropy changes, Sm in the temperature range T = 0 K to T = Tf have also been estimated. Values of Sm and the effective value of the magnetic spin number J were found to be less than the expected maximum values of Sm(max) = Rℓn(2J + 1) and the well-known value of the magnetic number J of the rare earth metal respectively. The apparent features of the present amorphous magnetic samples agree quite well with traditional behaviors of the condensed spin glass systems.