The nature of the first order isostructural transition in GdRhSn.

We present structural, magnetic, thermal, magnetocaloric, and electrical transport properties of polycrystalline GdRhSn. Magnetization data show that it orders antiferromagnetically at TN = 16.2 K. The compound has the ZrNiAl type hexagonal crystal structure at room temperature and undergoes a first order iso-structural transition in the paramagnetic state at 245 K. The unit cell volume change at the transition is small (-0.07%) but discontinuous, in agreement with the first-order nature of the transition observed by magnetic, transport, and heat capacity measurements. The anisotropic changes of the lattice parameters are Δa/a = 0.28% and Δc/c = -0.64% on cooling. A substantial change in the 4f and conduction electron hybridization, giving rise to an increased integrated DOS, occurs when the high temperature phase transforms to the low temperature phase. A moderate magnetocaloric effect at TN (ΔSM = -6.5 J/kg K and ΔTad = 4.5 K for ΔH = 50 kOe) has been measured using both magnetization and heat capacity data. [ABSTRACT FROM AUTHOR]