Magnetic, electrical and thermodynamic properties of NpIr: ambient and high pressure measurements, and electronic structure calculations

TL;DR

This study investigates the magnetic, electrical, thermodynamic, and electronic properties of NpIr through experiments and calculations, revealing it as a heavy fermion system with strong antiferromagnetic interactions and low thermal conductivity.

Contribution

It provides comprehensive experimental and theoretical analysis of NpIr's properties, including high-pressure behavior and electronic structure, which was previously unexplored.

Findings

NpIr is a moderately heavy fermion Kondo system.

No phase transition observed down to 0.55 K or at 17.3 GPa.

Predicted extremely low lattice thermal conductivity at high temperatures.

Abstract

We present bulk property measurements of NpIr, a newly synthesized member of the Np-Ir binary phase diagram, which is isostructural to the non-centrosymmetric pressure-induced ferromagnetic superconductor UIr. Magnetic susceptibility, electronic transport properties at ambient and high pressure, and heat capacity measurements have been performed for temperature T = 0.55 - 300 K, in a range of magnetic fields up to 14 T and under pressures up to 17.3 GPa. These reveal that NpIr is a moderately heavy fermion Kondo system with strong antiferromagnetic interactions, but there is no evidence of any phase transition down to 0.55 K or at the highest pressure achieved. Experimental results are compared with ab initio calculations of the electronic band structure and lattice heat capacity. An extremely low lattice thermal conductivity is predicted for NpIr at temperatures above 300 K.