Magnetic Structure and Effects of Pressure on U4PdGa12

We report on the magnetic structure, thermopower, compressibility, and electrical resistivity under pressure of the recently discovered heavy-fermion antiferromagnet U4PdGa12. The ordering temperature of the annealed polycrystalline U4PdGa12 is TN45.5 K. The magnetic structure has been investigated by neutron diffraction. Extra reflections in the powder spectrum appear below 46 K, in good agreement with macroscopic measurements. The simplest magnetic structure compatible with neutron-diffraction data is a collinear antiferromagnetic structure described by the propagation vector q=001. In this case the ordered uranium moment amounts to 1.01 6 B and point along the a axis. Thermopower confirms the heavy-fermion features in this uranium intermetallic with positive and high values of Seebeck coefficient. The magnetic transition is clearly identified and induces an upturn below 45.5 K which is followed by a continuous decrease in ST at lower temperature. Electrical resistivity measurements of U4PdGa12 under pressure of up to 13.5 GPa indicate the disappearance of the magnetic ordering temperature TN around Pc=10 GPa while compressibility measurements performed by x-ray diffraction up to 25 GPa do not show any structural phase transition related to this magnetic collapse. At higher pressure p10 GPa and at low temperature, a non-Fermi-liquid behavior is observed, with a T5/3 dependence of the resistivity. This suggests the possible occurrence of a quantum critical point near Pc.

JARDIN R.;  GRIVEAU Jean-Christophe;  PROKES K.;  GOFRYK Krzysztof;  KOLOMIETS A. V.;  NORMILE P.S.;  HEATHMAN Stephen;  COLINEAU Eric;  WASTIN Franck;  REBIZANT J.; 

2009-02-20

AMER PHYSICAL SOC

JRC50433

1098-0121,   

http://dx.doi.org/10.1103/PhysRevB.79.014409,    https://publications.jrc.ec.europa.eu/repository/handle/JRC50433,   

10.1103/PhysRevB.79.014409,