UNUSUAL LOW-TEMPERATURE SPECIFIC-HEAT IN TERNARY GD INTERMETALLIC COMPOUNDS

Specific heat measurements are reported for the alloy series Pd2GdxLa1 -x In for 0 less than or equal to x less than or equal to 1.0, and als o for Pd2LuIn and Cu2GdIn. A well defined anomaly associated with the onset of the magnetically ordered state is observed in the specific he at for Pd2GdIn at T = 9 K. As x decreases the anomaly becomes broader and the maximum reduces to a lower temperature. Measurements on the no n-magnetic compounds Pd2LaIn and PdlLuIn were made to isolate the magn etic contribution to the heat capacity of the Gd compounds. Such an an alysis reveals a significant magnetic contribution remaining at temper atures far above T-N ( > 2T(N)) for the compounds where x = 1.0, 0.75 and 0.50. The total magnetic entropy at 20 K is well in excess of the theoretical value of xR ln(8) for these compounds. Above 20 K magnetis ation measurements on Pd2GdIn show a Curie-Weiss behaviour and the abs ence of short range magnetic order, whilst the specific heat of Pd2GdI n is still enhanced at 30 K. Above 20 K the enhanced specific heat var ies linearly with temperature, suggesting a gamma-value of 202 mJ/K-2 mol. Subtraction of such a linear term over the entire temperature ran ge yields a magnetic entropy more consistent with that expected for Gd . For the S-state element Gd, the existing theories put forward to exp lain such an enhanced gamma-value on the basis of heavy fermion behavi our are not applicable. The possibility of an additional conduction el ectron contribution to the magnetic specific heat is supported by meas urements on Cu2GdIn, although the magnitude of the enhancement in Pd2G dIn is difficult to reconcile with this approach. (C) 1998 Elsevier Sc ience B.V. All rights reserved.