Heavy Fermion and non-Fermi Liquid Properties vs Size: From the Micro to the Nano*

Y. Y. Chen et al. have studied nanoparticles of several systems, including CePt$_{2}$ [1]. We report here the specific heat, C, down to 0.05 K and $\chi$ to 2 K as a function of size for several Ce- and U-heavy Fermion and non-Fermi liquid (nFl) systems, including UBe$_{13}$ and Rh-doped CeRu$_{2}$Si$_{2}$. Using dry sieves (for larger particles) and aqueous suspension/filtration techniques using Isopore$^{TM}$ filters (for smaller particles), size gradations from 45-53 $\mu$ (essentially bulk) down to 0.6-1.2 $\mu$ were studied. One goal was to study the evolution of nFl behavior vs decreasing size at a Quantum Critical Point, where the spatial extent of the fluctuations should become infinite, or at least larger than the particle at some size. Ce-systems showed the beginning of Kondo peak behavior in C below 3 $\mu$, however it was still possible to determine the evolution of the intrinsic low temperature nFl C/T $\sim$ logT in Rh-doped CeRu$_{2}$Si$_{2}$ as a function of decreasing size to address this goal. The effect of size on superconductivity and m$^{*}$ in UBe$_{13}$ will also be discussed.\\[0pt] [1] Y. Y. Chen et al., Phys. Rev. Lett. 98, 157206 (2007).