Field-induced non-Fermi-liquid behavior inCe2IrIn8

Abstract

In zero field, ${\mathrm{Ce}}_{2}{\mathrm{IrIn}}_{8}$ obeys Landau's Fermi-liquid model, with a constant $C/T$ of about 700 mJ/Ce mol ${\mathrm{K}}^{2}$ below 0.7 K and a susceptibility that is constant to \ifmmode\pm\else\textpm\fi{}4% below 4 K. In applied magnetic field, however, ${\mathrm{Ce}}_{2}{\mathrm{IrIn}}_{8}$ shows definite non-Fermi-liquid (nFl) behavior at \ensuremath{\sim}13 T, with $C/T\ensuremath{\sim}\mathrm{ln}T$ between 0.3 and 6 K, $\ensuremath{\chi}\ensuremath{\sim}\mathrm{ln}T,$ and $\ensuremath{\rho}={\ensuremath{\rho}}_{0}{+AT}^{1}.$ At fields of 17 T and higher there is a strong divergent upturn in $C/T$ below 0.7 K that is approximately field independent and the susceptibility becomes again constant (Fermi-liquid like) below 6 K and decreases in magnitude at low temperature compared to \ensuremath{\chi} (13 T). These results imply that a quantum critical point may exist in ${\mathrm{Ce}}_{2}{\mathrm{IrIn}}_{8}$ at \ensuremath{\sim}13 T. The magnetization at low temperature as a function of field of ${\mathrm{Ce}}_{2}{\mathrm{IrIn}}_{8}$ between 0.1 and 30 T shows no sign of an increase, or jump, near 13 T, but rather a change from $M\ensuremath{\sim}H$ at lower fields to a more saturated behavior above 13 T. Thus, unlike previous field-induced nFl behavior, where the magnetic interactions responsible for the nFl behavior either came (i) at the field, ${H}_{\mathrm{metamag}},$ where the magnetization showed a step at a metamagnetic transition (e.g., in ${\mathrm{UPt}}_{3}$ or in ${\mathrm{Sr}}_{3}{\mathrm{Ru}}_{2}{\mathrm{O}}_{7}),$ or (ii) at the field where ${T}_{\mathrm{N}\mathrm{\'e}\mathrm{el}}$ in an antiferromagnet was suppressed to $T=0$ by the field (e.g., in ${\mathrm{CeCu}}_{6\ensuremath{-}x}{\mathrm{Ag}}_{x}),$ the present measurements point to a different kind of behavior. Thus the nFl behavior in ${\mathrm{Ce}}_{2}{\mathrm{IrIn}}_{8}$ may be describable as due to quantum criticality at the point in the phase diagram where field induces magnetism. Comparisons to other nFl systems, both field-induced and those which display an anomalous upturn in $C/T$ at low temperatures, are made.