Incipient magnetic order inCeCu6

Low-field (0.8 Oe), low-temperature (60 mK–2 K) static magnetic susceptibility (χ) measurements on a series of Ce(${\mathrm{Cu}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Ag}}_{\mathrm{x}}$ ${)}_6$ compounds with x≤0.20 reveal magnetic transitions characterized by maxima in χ at well-defined temperatures for the x=0.05 and 0.10 samples. All samples show marked differences between the magnetic field-cooled and zero-field-cooled data. A sharp anomaly in the specific heat for the x=0.10 sample at nearly the same temperature as the maximum in χ points toward an antiferromagnetic transition, whereas magnetization data for the x=0.15 and 0.20 samples are indicative of ferrimagnetic or ferromagnetic order. The data indicate a change from antiferromagnetic to ferrimagnetic or ferromagnetic order with increasing Ag concentration. The dependence of the magnetic ordering temperature on concentration x reveals that extremely small (∼1.3 at. %) amounts of Ag impurity are sufficient to induce magnetic order in ${\mathrm{CeCu}}_6$. The relevance of these results to the properties of ${\mathrm{CeCu}}_6$ is discussed.