Evolution of the partially frustrated magnetic order in CePd$_{1-x}$Ni$_x$Al

TL;DR

This study investigates how antiferromagnetic order evolves in the heavy-fermion compound CePd$_{1-x}$Ni$_x$Al with partial geometric frustration, revealing a consistent magnetic structure and the suppression of magnetic moments near a quantum critical point.

Contribution

It provides detailed neutron diffraction data showing the magnetic structure remains unchanged across Ni doping levels and characterizes the suppression of magnetic order near the quantum critical point.

Findings

Magnetic structure remains unchanged with Ni doping up to x_c.

Ordered magnetic moments vanish linearly with T_N near x_c.

Substantial short-range correlations persist above T_N due to frustration.

Abstract

We report on a single-crystal neutron diffraction study of the evolution of the antiferromagnetic order in the heavy-fermion compound CePd$_{1-x}$Ni$_x$Al which exhibits partial geometric frustration due to its distorted Kagom\'e structure. The magnetic structure is found to be unchanged with a propagation vector $Q_\mathrm{AF} \approx (0.5~0~0.35)$ for all Ni concentrations $x$ up to $x_c \approx 0.14$. Upon approaching the quantum critical concentration $x_c$, the ordered moment vanishes linearly with N\'eel temperature $T_{\rm N}$, in good agreement with CePdAl under hydrostatic pressure. For all Ni concentrations, substantial short-range magnetic correlations are observed above $T_{\rm N}$ as a result of frustration.