Enhancement of heat capacity above the Néel temperature in Gd_1−xY_xNi₂Si₂ alloys, and its implications

Abstract

The results of heat-capacity (C) measurements on the alloys Gd_1−xY_xNi₂Si₂ in the temperature interval 2-30 K are reported. The Gd contribution to the heat capacity (C_m) 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 Gd_0.4Y_0.6Ni₂Si₂, for which the Néel temperature is about 5 K, C_m 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 C_m 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.