Switching of magnetic ground states across the UIr1-xRhxGe alloy system

TL;DR

This study maps the magnetic phase transitions in the UIr1-xRhxGe alloy system, revealing a discontinuous magnetic boundary and field-induced transitions, but no quantum critical point.

Contribution

It provides a detailed phase diagram and insights into magnetic fluctuations and transitions across the alloy system, highlighting the absence of a quantum critical point.

Findings

Discontinuous antiferromagnetic/ferromagnetic boundary at x=0.56

Maximum magnetic fluctuations near x=0.56

Field-induced first order transition observed

Abstract

We investigated the evolution of magnetism in the UIr1-xRhxGe system by the systematic study of high-quality single crystals. Lattice parameters of both parent compounds are very similar resulting in almost identical nearest interatomic uranium distance close to the Hill limit. We established the x-T phase diagram of the UIr1-xRhxGe system and found a discontinuous antiferromagnetic/ferromagnetic boundary at xcrit = 0.56 where a local minimum in ordering temperature and maximum of the Sommerfeld coefficient 175 mJ/mol K2 occurs in the UCoGe-URhGe-UIrGe system, signaling an increase in magnetic fluctuations. However, a quantum critical point is not realized because of the finite ordering temperature at xcrit. A magnon gap on the antiferromagnetic side abruptly suppresses magnetic fluctuations. We find a field-induced first order transition in the vicinity of the critical magnetic field along the b axis in the entire UIr1-xRhxGe system including the ferromagnetic region UCo0.6Rh0.4Ge - URhGe.