Avoided ferromagnetic quantum critical point in CeRuPO

TL;DR

This study investigates how pressure influences magnetic ordering in CeRuPO, revealing a transition from ferromagnetic to antiferromagnetic states and the absence of a quantum critical point due to abrupt changes in magnetic properties.

Contribution

It demonstrates that CeRuPO avoids a ferromagnetic quantum critical point through a pressure-induced magnetic transition and changes in electronic structure, providing insights into quantum criticality suppression.

Findings

Magnetic order changes from FM to AFM at ~0.87 GPa

No quantum critical point observed up to 7.5 GPa

LFL behavior persists across the pressure range

Abstract

CeRuPO is a rare example of a ferromagnetic (FM) Kondo-lattice system. External pressure suppresses the ordering temperature to zero at about $p_c\approx3$ GPa. Our ac-susceptibility and electrical-resistivity investigations evidence that the type of magnetic ordering changes from FM to antiferromagnetic (AFM) at about $p^*\approx0.87$ GPa. Studies in applied magnetic fields suggest that ferromagnetic and antiferromagnetic correlations compete for the ground state at $p>p^*$, but finally the AFM correlations win. The change in the magnetic ground-state properties is closely related to the pressure evolution of the crystalline-electric-field level (CEF) scheme and the magnetic Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange interaction. The N\'{e}el temperature disappears abruptly in a first-order-like fashion at $p_c$, hinting at the absence of a quantum critical point. This is consistent with the low-temperature transport properties exhibiting Landau-Fermi-liquid (LFL) behavior in the whole investigated pressure range up to 7.5 GPa.