Pressure effects on magnetism in U intermetallics: the UPtAl case

The influence of pressure on the formation of U magnetic moments and mediation of exchange interactions are two principal aspects of the complex role of the 5f-ligand hybridization in magnetism of U intermetallics. Application of external pressure yields changes of interatomic distances, which are the crucial parameters controlling the hybridization. We report on pressure experiments with a 5f-electron ferromagnet UPtAl (T C=42.5 K, M s=1.4 μ B/f.u. at ambient pressure). Application of hydrostatic pressure up to 1 GPa yields decrease of the spontaneous magnetization M s with a rate dM s/dp=-0.027 μ B/GPa, whereas T C increases (dT C/dp=2.5 K/GPa). Extension of the electrical resistivity measurements of UPtAl to pressures up to 22 GPa reveals that the initial increase of T C with pressure continues up to 6 GPa, where T C reaches the maximum value, and decreases with further increasing pressure. The drastic change of the R(T) curve at 17 GPa is presumably connected with suppression of ferromagnetism in UPtAl