High pressure investigation of the heavy-fermion antiferromagnet U_3Ni_5Al_19

TL;DR

This study investigates how applying pressure affects the magnetic, thermal, and electrical properties of the heavy-fermion antiferromagnet U_3Ni_5Al_19, revealing quantum critical points and magnetic instabilities.

Contribution

It provides the first detailed high-pressure measurements on U_3Ni_5Al_19, identifying quantum critical behavior and magnetic phase transitions in this compound.

Findings

Observation of non-Fermi liquid behavior at ambient pressure.

Detection of a crossover from NFL to Fermi liquid at 46-51 kbar.

Identification of a second antiferromagnetic instability at 60 kbar.

Abstract

Measurements of magnetic susceptibility, specific heat, and electrical resistivity at applied pressures up to 55 kbar have been carried out on single crystals of the heavy-fermion antiferromagnet U_3Ni_5Al_19, which crystallizes in the Gd_3Ni_5Al_19 orthorhombic structure with two inequivalent U sites. At ambient pressure, a logarithmic T-dependence of the specific heat and T-linear electrical resistivity below 5 K indicates non-Fermi liquid (NFL) behavior in the presence of bulk antiferromagnetic order at T_N=23 K. Electrical resistivity measurements reveal a crossover from non-Fermi liquid to Fermi liquid behavior at intermediate pressures between 46 kbar and 51 kbar, followed by a return to NFL T^{3/2} behavior at higher pressures. These results provide evidence for an ambient pressure quantum critical point and an additional antiferromagnetic instability at P_c=60 kbar.