Mass-Enhanced Fermi Liquid Ground State in Na${}_{1.5}$Co${}_2$O${}_4$

Abstract

Magnetic, transport, and specific heat measurements have been performed on layered metallic oxide Na${}_{1.5}$Co${}_2$O${}_4$ as a function of temperature $T$. Below a characteristic temperature $T^{\ast }$=30$-$40 K, electrical resistivity shows a metallic conductivity with a $T^2$ behavior and magnetic susceptibility deviates from the Curie-Weiss behavior showing a broad peak at $\sim$14 K. The electronic specific heat coefficient $\gamma$ is $\sim$60 mJ/molK${}^2$ at 2 K. No evidence for magnetic ordering is found. These behaviors suggest the formation of mass-enhanced Fermi liquid ground state analogous to that in $d$-electron heavy fermion compound LiV${}_2$O${}_4$.

4 pages, 4 figures, to be published in Phys. Rev. B 69 (2004)