Theory of magnetism for rare-earth magnets on the Shastry-Sutherland lattice with non-Kramers ions

TL;DR

This paper develops an effective spin model for non-Kramers ions in rare-earth Shastry-Sutherland magnets, revealing hidden quadrupole orders and a possible 1/3 magnetization plateau, with implications for specific materials.

Contribution

It introduces a novel extended XYZ model with intrinsic fields for non-Kramers moments on the Shastry-Sutherland lattice and explores hidden quadrupole phases.

Findings

Pure quadrupole orders can be stabilized over broad regimes.

A hidden 1/3 magnetization plateau with quadrupole order exists.

Relevance to Pr$_{2}$Ga$_{2}$BeO$_{7}$ and Pr$_{2}$Be$_{2}$GeO$_{7}$ materials.

Abstract

Motivated by the rapid experimental progress on the rare-earth Shastry-Sutherland lattice magnets, we propose a generic effective spin model that describes interacting non-Kramers local moments on the Shastry-Sutherland lattice. We point out that the local moments consist of both magnetic dipole and quadrupole components and the effective model turns out to be an extended XYZ model with an intrinsic field that accounts for the crystal field splitting. We then study the ground-state phase diagram of the model and find that pure quadrupole orders, which are invisible to conventional experimental probes, can be stabilized over a broad regime. In particular, we show that a hidden ``1/3 magnetization plateau'' with quadrupole orders generally exists and discuss its experimental signatures. Finally, we discuss the relevance of our results to the rare-earth Shastry-Sutherland lattice magnets Pr$_{2}$Ga$_{2}$BeO$_{7}$ and Pr$_{2}$Be$_{2}$GeO$_{7}$.