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

Using Ag doping of the nearly magnetic heavy-fermion system ${\mathrm{CeCu}}_6$ to vary the onset of antiferromagnetism between $T_N=0\mathrm{}$ and 0.8 K, we have found a large region of the phase diagram where magnetic field can reach the quantum critical point ${(T}_N\to 0)$ with sufficiently strong antiferromagnetic correlations remaining to produce non-Fermi-liquid (NFL) behavior. In this field and composition regime, the ${\mathrm{CeCu}}_{6-x}{\mathrm{Ag}}_x$ 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.