About the origin of the magnetic ground state of Tb$_{2}$Ir$_{2}$O$_{7}$

TL;DR

This study investigates the unusual magnetic ground state of Tb$_{2}$Ir$_{2}$O$_{7}$, revealing a complex magnetic ordering and excitation spectrum driven by interactions between rare-earth and iridium ions, using neutron scattering and theoretical modeling.

Contribution

It provides new insights into the magnetic ordering of Tb$_{2}$Ir$_{2}$O$_{7}$ and demonstrates the importance of bilinear interactions and additional factors in explaining its magnetic behavior.

Findings

Magnetic state fully established at 1.5 K

Excitation spectrum characterized across broad energies

Bilinear interactions partially reproduce experimental features

Abstract

Magnetic-rare-earth pyrochlore iridates exhibit a rich variety of unconventional phases, driven by the complex interactions within and between the rare-earth and the iridium sublattices. In this study, we investigate the peculiar magnetic state of Tb$_{2}$Ir$_{2}$O$_{7}$, where a component of the Tb$^{3+}$ moment orders perpendicular to its local Ising anisotropy axis. By means of neutron diffraction and inelastic neutron scattering down to dilution temperatures, complemented by specific heat measurements, we show that this intriguing magnetic state is fully established at 1.5 K and we characterize its excitation spectrum across a broad range of energies. Our calculations reveal that bilinear interactions between Tb$^{3+}$ ions subjected to the Ir molecular field capture several key features of the experiments, but need to be supplemented to fully reproduce the observed behavior.