Approaching quantum criticality in a partially geometrically frustrated heavy-fermion metal

In the antiferromagnetic (AF) heavy-fermion system CePdAl the magnetic Ce ions form a network of equilateral triangles in the (001) plane, similar to the kagome lattice, with one third of the Ce moments not participating in the long-range order. The Neel temperature T-N = 2.7 K is reduced upon replacing Pd by Ni in CePd1-xNixAl, with T-N -> 0 for x = 0.144, where the specific heat C exhibits a C/T proportional to - log T dependence. Within the Hertz-Millis-Moriya model of quantum criticality, this behavior might indicate 2D critical antiferromagnetic fluctuations arising from the decoupling of 3D magnetic order by frustration. On the other hand, the simultaneous presence of Kondo effect and geometric frustration might entail a different route to quantum criticality.