Effect of Ce Dilution on the Ferromagnetic Ordering in CeAuGe

Transport and thermodynamic properties of the well-ordered hexagonal CeAuGe compound have been studied. This compound is known to order ferromagnetically at T-C = 10 K with well-defined anomalies in magnetic susceptibility chi(T), electrical resistivity rho(T) and specific heat C-p(T) characterising the phase transition. The location of Tc has been observed to be unstable and enhanced even in moderate applied magnetic fields. However, the dilution of magnetic species, Ce, with the non-f electron element, La, is shown in this work to achieve a continuous suppression of T-C to 0 K. The integrity of the space group and the details of the unit cell occupation are retained throughout the substitution series, as is the high-temperature localized Ce-effective magnetic moment mu(eff) = 2.54 mu(B) /(mol Ce). Our studies of physical properties down to 0.05 K show a quantum critical form of nonFermi liquid behaviour, characterised by a logarithmic divergence in C-p(T)/T data in the very dilute Ce content.