Evidence for persistent spin fluctuations in uranium sesquicarbide

The low-temperature magnetic susceptibility, heat capacity and electrical resistivity of uranium sesquicarbide have been estimated down to 2 K by combining measurements carried out on samples of U2C3, containing UC as minority phase, and on pure UC specimens. The presence of spin fluctuations with characteristic temperature TSF = 7 K is revealed by a nonanalytic contribution to the specific heat behaving (well below TSF ) as T3ln(T=TSF ), and confirmed by a T2 increase of the electrical resistivity and a 1 - T2 decrease of the low-temperature magnetic susceptibility. The analysis of the specific heat data above TSF provides a Debye temperature ΘD 256 K and a moderately high value of the Sommerfeld coefficient, 42.4 mJmol U -1 K-2. The zero-temperature many-body enhancement of the electron mass is found to be m*/m 2.7. Our data rule out the occurrence of magnetic ordering in U2C3. First principles electronic structure calculations support the absence of a magnetically ordered ground state but suggest that dynamical spin fluctuations are responsible for the electron mass enhancement.

ELOIRDI Rachel;  FUCHS Andreas;  GRIVEAU Jean-Christophe;  COLINEAU Eric;  SHICK A.B.;  MANARA Dario;  CACIUFFO Roberto; 

2014-03-03

Dipartimento di Chimica e Chimica Industriale (DCCI) , Università di Genova

JRC79918