Excess Magnetic Susceptibility Arising from Self damage in Alpha-Pu

The $f-$electrons of plutonium are delicately poised on the edge between localized and itinerant behavior. In the case of $\alpha -$Pu, the electrons are nearly localized in a narrow $f-$band and the Pauli magnetic susceptibility is the largest of any element. Low temperature magnetic susceptibility measurements on $\alpha -$Pu show that the magnetic susceptibility increases as a function of time, yet upon annealing the specimen at 350K, it returns to its initial value. This suggests that the excess magnetic susceptibility,\textit{ $\chi $}$_{xs}(t,T)$, arises from the $\alpha $-decay and U recoil damage cascades which produce vacancy and interstitials as point and extended defects. The time dependence of \textit{$\chi $}$_{xs}$ is well described by \textit{$\chi $}$_{xs}$\textit{$\sim $a(1-exp(-t/$\tau )$}) where $a$ and \textit{$\tau $} are both functions of temperature. At short times, \textit{$\chi $}$_{xs}$\textit{(T$<$30),} may be fit to a Curie-Weiss law. However, as \textit{t--$>\infty $}, \textit{$\chi $}$_{xs}$\textit{(T$<$30) --$>$ T}$^{-1}$ implying that self-damage may drive Pu towards non-Fermi liquid behavior. \textit{This work was performed under the auspices of the U. S. DOE by Lawrence Livermore National Laboratory, under contract W-7405-Eng-48.}