We have measured X-ray magnetic circular dichroism (XMCD) spectra at the Pu M4;5 absorption edges from a newly-prepared high-quality single crystal of the heavy fermion superconductor 242PuCoGa5, exhibiting a critical temperature Tc = 18.7 K. The experiment probes the vortex phase below Tc and shows that an external magnetic field induces a Pu 5f magnetic moment at 2 K equal to the temperature-independent moment measured in the normal phase up to 300 K by a SQUID device. This observation is in agreement with theoretical models claiming that the Pu atoms in PuCoGa5 have a nonmagnetic singlet ground state resulting from the hybridization of the conduction electrons with the intermediate-valence 5f electronic shell. Unexpectedly, XMCD spectra show that the orbital component of the 5f magnetic moment increases significantly between 30 and 2 K; the antiparallel spin component increases as well, leaving the total moment practically constant. We suggest that this indicates a low-temperature breakdown of the complete Kondo-like screening of the local 5f moment.
MAGNANI Nicola;
ELOIRDI Rachel;
WILHELM F.;
COLINEAU Eric;
GRIVEAU Jean-Christophe;
SHICK Alexander B.;
LANDER G. H.;
ROGALEV A.;
CACIUFFO Roberto;
2017-10-26
AMER PHYSICAL SOC
JRC106938
0031-9007,
https://publications.jrc.ec.europa.eu/repository/handle/JRC106938,
10.1103/PhysRevLett.119.157204,
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