Enhancement of heat capacity above the Néel temperature in Gd1-xYxNi2Si2 alloys, and its implications.

Abstract

The results of heat-capacity (C) measurements on the alloys ${\mathrm{Gd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Y}}_{\mathit{x}}$${\mathrm{Ni}}_{2}$${\mathrm{Si}}_{2}$ in the temperature interval 2--30 K are reported. The Gd contribution to the heat capacity (${\mathit{C}}_{\mathit{m}}$) shows a strong increase with decreasing temperature before the Gd sublattice orders magnetically, resembling the behavior in Ce-based heavy-fermion antiferromagnets. For instance, in the case of the alloy ${\mathrm{Gd}}_{0.4}$${\mathrm{Y}}_{0.6}$${\mathrm{Ni}}_{2}$${\mathrm{Si}}_{2}$, for which the N\'eel temperature is about 5 K, ${\mathit{C}}_{\mathit{m}}$ varies as ${\mathit{T}}^{\mathrm{\ensuremath{-}}2}$ (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 ${\mathit{C}}_{\mathit{m}}$ 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.