Magnetic properties of the quasi-XY Shastry-Sutherland magnet Er$_2$Be$_2$SiO$_7$

TL;DR

This study investigates the magnetic properties and phase diagrams of Er$_2$Be$_2$SiO$_7$, revealing a non-collinear ground state, complex field-induced transitions, and potential for exotic magnetic phenomena aligned with the Shastry-Sutherland model.

Contribution

First comprehensive analysis of Er$_2$Be$_2$SiO$_7$'s magnetic structure, phase behavior, and anisotropy, linking experimental findings to theoretical models of the Shastry-Sutherland system.

Findings

Crystallizes in tetragonal space group with orthogonal Er dimers.

Exhibits non-collinear antiferromagnetic ground state below 0.841 K.

Displays multiple metamagnetic transitions under in-plane magnetic fields.

Abstract

Polycrystalline and single crystal samples of the insulating Shastry-Sutherland compound Er$_2$Be$_2$SiO$_7$ were synthesized via a solid-state reaction and the floating zone method respectively. The crystal structure, Er single ion anisotropy, zero-field magnetic ground state, and magnetic phase diagrams along high-symmetry crystallographic directions were investigated by bulk measurement techniques, x-ray and neutron diffraction, and neutron spectroscopy. We establish that Er$_2$Be$_2$SiO$_7$ crystallizes in a tetragonal space group with planes of orthogonal Er dimers and a strong preference for the Er moments to lie in the local plane perpendicular to each dimer bond. We also find that this system has a non-collinear ordered ground state in zero field with a transition temperature of 0.841 K consisting of antiferromagnetic dimers and in-plane moments. Finally, we mapped out the $H-T$ phase diagrams for Er$_2$Be$_2$SiO$_7$ along the directions $H \parallel$ [001], [100], and [110]. While an increasing in-plane field simply induces a phase transition to a field-polarized phase, we identify three metamagnetic transitions before the field-polarized phase is established in the $H \parallel$ [001] case. This complex behavior establishes insulating Er$_2$Be$_2$SiO$_7$ and other isostructural family members as promising candidates for uncovering exotic magnetic properties and phenomena that can be readily compared to theoretical predictions of the exactly soluble Shastry-Sutherland model.