Fractionalized Magnetization Plateaus in the Shastry-Sutherland Lattice Material Er$_2$Be$_2$GeO$_7$

TL;DR

This study reports the observation of fractionalized magnetization plateaus in Er$_2$Be$_2$GeO$_7$, a Shastry-Sutherland lattice material, accessible at low fields and exhibiting long-range magnetic order, making it ideal for studying frustrated magnetism.

Contribution

The paper introduces Er$_2$Be$_2$GeO$_7$ as a new Shastry-Sutherland lattice material showing fractionalized magnetization plateaus at low fields with long-range order, unlike previous compounds.

Findings

Fractionalized magnetization plateaus at 1/4 and 1/2 of full moment.

Plateaus occur at fields below 1 Tesla, accessible with standard lab equipment.

The 1/4 plateau has a classical canted antiferromagnetic structure.

Abstract

The experimental study of magnetism on the Shastry-Sutherland lattice has been ongoing for more than two decades, following the discovery of the first Shastry-Sutherland lattice materials SrCu$_2$(BO$_3$)$_2$. However, the study of Shastry-Sutherland systems is often complicated by the requirements of high magnetic fields ($>$~20~T SrCu$_2$(BO$_3$)$_2$) or the presence of itinerate electrons (e.g. REB$_4$). In this paper, we present the magnetic properties of the Shastry-Sutherland lattice material Er$_2$Be$_2$GeO$_7$. Like SrCu$_2$(BO$_3$)$_2$, Er$_2$Be$_2$GeO$_7$ exhibits fractionalized magnetization plateaus. Unlike SrCu$_2$(BO$_3$)$_2$, Er$_2$Be$_2$GeO$_7$ exhibits long-range order below $\sim1~$K, and the plateaus are accessible using commercial laboratory equipment, occurring for fields <~1~T. The fractions of magnetization present are closest to $\frac{1}{4}$ and $\frac{1}{2}$ of the full powder moment; we show that the $\frac{1}{4}$ magnetization plateau in Er$_2$Be$_2$GeO$_7$ has a classical analog, well represented by the magnetic structure (canted antiferromagnetic) observed in powder neutron diffraction. The lack of itinerate electrons, chemical disorder, and the low fields required to access the fractionalized magnetization plateaus promises Er$_2$Be$_2$GeO$_7$ to be a prime candidate for the study of frustrated magnetism on the Shastry-Sutherland lattice.