Evolution of the partially frustrated magnetic order in CePd 1 − x Ni x Al6212

We report on a single-crystal neutron-diffraction study of the evolution of the antiferromagnetic order in the heavy-fermion compound CePd1−xNixAl which exhibits partial geometric frustration due to its distorted kagome structure. The magnetic structure is found to be unchanged with a propagation vector QAF≈(0.500.35) for all Ni concentrations x up to xc≈0.14. Upon approaching the quantum critical concentration xc, the ordered moment vanishes linearly with Néel temperature TN, in good agreement with CePdAl under hydrostatic pressure. For all Ni concentrations, substantial short-range magnetic correlations are observed above TN as a result of frustration