Inducement of non-Fermi-liquid behavior with a magnetic field

Abstract

Using Ag doping of the nearly magnetic heavy-fermion system ${\mathrm{CeCu}}_{6}$ to vary the onset of antiferromagnetism between ${T}_{N}=0$ and 0.8 K, we have found a large region of the phase diagram where magnetic field can reach the quantum critical point ${(T}_{N}\ensuremath{\rightarrow}0)$ with sufficiently strong antiferromagnetic correlations remaining to produce non-Fermi-liquid (NFL) behavior. In this field and composition regime, the ${\mathrm{CeCu}}_{6\ensuremath{-}x}{\mathrm{Ag}}_{x}$ samples exhibit the typical NFL temperature dependencies for the various measured parameters over a broad range of temperature down to 100 mK. Application of higher fields to these samples causes entry into the Fermi-liquid regime. Due to the ease of changing magnetic fields when establishing the phase diagram at low temperatures, the increased efficacy of field suppression of ${T}_{N}$ versus that achieved by pressure, and the fact that magnetic field does not change the volume as do both pressure and doping, magnetic field offers distinct advantages as a method for exploring the crossover between antiferromagnetic, non-Fermi-liquid, and Fermi-liquid behavior in the vicinity of the quantum critical point.