Approaching Quantum Criticality in ferromagnetic Ce_2 (Pd_1-x Rh_x)_2 In alloys

TL;DR

This study investigates how doping Ce_2.15 (Pd_1-x Rh_x)_1.95 In_0.9 alloys influences their magnetic properties and explores the emergence of a quantum critical point through thermal and magnetic measurements.

Contribution

It demonstrates the tuning of magnetic phase transitions and the identification of a quantum critical point in Ce-based alloys via Rh doping.

Findings

Magnetic transition temperature decreases with Rh doping.

Splitting of magnetic transition into AF and FM phases.

Quantum critical behavior observed near x ~ 0.5-0.55.

Abstract

Low temperature magnetic and thermal (C_m) properties of the ferromagnetic (FM) alloys Ce_2.15 (Pd_1-x Rh_x)_1.95 In_0.9 were investigated in order to explore the possibility for tuning a quantum critical point (QCP) by doping Pd with Rh. As expected, the magnetic transition observed at T = 4.1K in the parent alloy decreases with increasing Rh concentration. Nevertheless it splits into two transitions, the upper being antiferromagnetic (AF) whereas the lower FM. The AF phase boundary extrapolates to T_N = 0 for x_cr ~ 0.65 whereas the first order FM transition vanishes at x ~ 0.3. The QC character of the T_N => 0 point arises from the divergent T dependence of the tail of C_m/T observed in the x = 0.5 and 0.55 alloys, and the tendency to saturation of the maximum of C_m(T_N)/T as observed in exemplary Ce compounds for T_N => 0. Beyond the critical concentration the unit cell volume deviates from the Vegard's law in coincidence with a strong increase of the Kondo temperature.