Magnetic structure, excitations and field induced transitions in the honeycomb lattice $\mathrm{E}{\mathrm{r}}_2\mathrm{S}{\mathrm{i}}_2{\mathrm{O}}_7$

Abstract

We investigate the magnetic properties of the monoclinic D-type $\mathrm{E}{\mathrm{r}}_2\mathrm{S}{\mathrm{i}}_2{\mathrm{O}}_7$ with a distorted honeycomb lattice using powder and single crystal neutron scattering techniques, as well as single crystal magnetisation measurements. The powder neutron diffraction shows that below the ordering temperature, $T_{\mathrm{N}}=1.85$ K, the compound forms a $\mathbf{q}=0$ antiferromagnetic structure with four sublattices. For $H\parallel a$, magnetisation measurements reveal a narrow, but clearly visible plateau at one third of the magnetisation saturation value. The plateau's stabilisation is accompanied by a significant increase of the magnetic unit cell, as the magnetic peaks with fractional indices are observed in single crystal neutron diffraction experiments. At low-temperatures, the inelastic neutron scattering measurements reveal the presence of low-energy dispersionless excitations. Their spectrum is sensitive to the applied field, it significantly softens on the magnetisation plateau, and demonstrates the behaviour expected for a non-collinear Ising antiferromagnet away from the plateau.

10 pages, 11 figures and Supplementary Material containing 8 pages, 6 figures. To view the .mcif file, please download and extract the gzipped tar source file listed under "Other formats"