Abstrakt
We established the basic electronic properties of zeta-Pu19Os, which is a close analogue to beta-Pu, and its low-temperature variety, eta-Pu19Os. Their magnetic susceptibility is 15% higher than for delta-Pu.
A specific heat study of zeta-Pu19Os shows a soft lattice similar to delta-Pu, leading to a low Debye temperature Theta(D) = 101 K. The linear electronic coefficient gamma related to the quasiparticle density of states at the Fermi level points to a higher value, 55 +/- 2 mJ (mol Pu K-2)(-1), compared to 40 mJ (mol K-2)(-1) for delta-Pu.
The results confirm that beta-Pu is probably the most strongly correlated Pu phase, as had been indicated by resistivity measurements. The volume and related Pu-Pu spacing is clearly not the primary tuning parameter for Pu metal, as the beta-Pu density stands close to the ground-state alpha-phase and is much higher than that for delta-Pu.
The eta-Pu19Os phase has a record gamma-value of 74 +/- 2 mJ (mol Pu K-2)(-1). The enhancement is not reproduced by LDA+DMFT calculations in the fcc structure, which suggests that multiple diverse sites can be the key to the understanding of beta-Pu.