Signature of frustrated moments in quantum critical CePd$_{1-x}$Ni$_x$Al

TL;DR

This study investigates quantum critical behavior and magnetic frustration in CePd$_{1-x}$Ni$_x$Al, revealing field-induced quantum criticality and signatures of frustrated moments through specific heat and magnetic Grüneisen parameter measurements.

Contribution

It demonstrates the emergence of two-dimensional quantum criticality and identifies signatures of frustrated moments in a kagomé lattice system with Kondo physics.

Findings

Quantum criticality occurs at a critical concentration around x=0.15.

Two-dimensional AF quantum criticality is observed at certain Ni concentrations.

Additional magnetic contributions near 2.5 T are linked to frustrated Ce moments.

Abstract

CePdAl with Ce $4f$ moments forming a distorted kagom\'e network is one of the scarce materials exhibiting Kondo physics and magnetic frustration simultaneously. As a result, antiferromagnetic (AF) order setting in at $T_{\mathrm{N}} = 2.7$~K encompasses only two thirds of the Ce moments. We report measurements of the specific heat, $C$, and the magnetic Gr\"uneisen parameter, $\Gamma_{\rm mag}$, on single crystals of CePd$_{1-x}$Ni$_x$Al with $x\leq 0.16$ at temperatures down to 0.05~K and magnetic fields $B$ up to $8$~T. Field-induced quantum criticality for various concentrations is observed with the critical field decreasing to zero at $x_c\approx 0.15$. Remarkably, two-dimensional (2D) AF quantum criticality of Hertz-Millis-Moriya type arises for $x=0.05$ and $x=0.1$ at the suppression of 3D magnetic order. Furthermore, $\Gamma_{\rm mag}(B)$ shows an additional contribution near $2.5$~T for all concentrations which is ascribed to correlations of the frustrated one third of Ce moments.