Specific heat in some gadolinium compounds. I. Experimental

Specific-heat measurements have been performed on the gadolinium compounds ${\mathrm{GdCu}}_2$ ${\mathrm{Si}}_2$, ${\mathrm{GdNi}}_2$ ${\mathrm{Si}}_2$, ${\mathrm{GdGa}}_2$, and ${\mathrm{GdCu}}_5$ in order to investigate the phase transitions between paramagnetic and commensurate or incommensurate antiferromagnetic states. Various shapes of specific-heat curves are observed at and below the ordering temperature ${\mathit{T}}_{\mathit{N}}$. In particular, the specific-heat discontinuity at ${\mathit{T}}_{\mathit{N}}$ is strongly reduced in the incommensurate systems. This behavior is related to the exact type of magnetic arrangement involved.