ENHANCEMENT OF HEAT-CAPACITY ABOVE THE NEEL TEMPERATURE IN GD1-XYXNI2SI2 ALLOYS, AND ITS IMPLICATIONS

The results of heat-capacity (C) measurements on the alloys Gd1-xYxNi2Si2 in the temperature interval 2-30 K are reported. The Gd contribution to the heat capacity (Cm) shows a strong increase with decreasing temperature before the Gd sublattice orders magnetically, resembling the behavior in Ce-based heavy-fermion antiferromagnets. For instance, in the case of the alloy Gd0.4Y0.6Ni2Si2, for which the Néel temperature is about 5 K, Cm varies as T-2 (where T is the temperature) below 25 K. There is a tendency of isothermal magnetization data in the paramagnetic state to saturate with the application of the magnetic field. The existence of short-range ferromagnetic correlations over an unusually wide temperature range so as to cause a heavy-fermion-like Cm anomaly is clearly brought out through these observations. The findings emphasize the need to consider such magnetic precursor effects while interpreting the C data of f-electron materials. © 1995 The American Physical Society.