Magnetic properties of the zigzag ladder compound SrTb2O4

TL;DR

This study investigates the magnetic properties of SrTb2O4, revealing a disordered ground state with weak correlations and field-induced magnetic order, using neutron diffraction, spectroscopy, magnetisation, and heat capacity measurements.

Contribution

It provides the first detailed neutron scattering analysis of SrTb2O4, demonstrating its nonmagnetic ground state despite strong magnetic interactions.

Findings

No magnetic order down to 35 mK.

Weak spin-spin correlations in ground state.

Field induces magnetic Bragg peaks with moments aligned along the field.

Abstract

We report on the properties of SrTb2O4, a frustrated zigzag ladder antiferromagnet, studied by single crystal neutron diffraction (with polarised neutrons in zero field and unpolarised neutrons in an applied magnetic field), as well as by neutron spectroscopy on a polycrystalline sample. The neutron scattering results are supported by single crystal magnetisation and heat capacity measurements. In zero field, neutron diffraction data show no transition to a magnetically ordered state down to the lowest experimentally available temperature of 35 mK, and the material remains magnetically disordered down to this temperature. Polarised neutron diffraction measurements reveal the presence of a diffuse scattering signal suggesting only very weak spin-spin correlations in the ground state. For H // c (the easy magnetisation direction), we followed the magnetisation process using neutron diffraction measurements and observed the appearance of field-induced magnetic Bragg peaks with integer h and k indices in the (hk0) scattering plane. No magnetic peaks with a non-zero propagation vector were detected. The observed in-field data fit well to a simple two-sublattice model with magnetic moments aligned along the field direction but being significantly different in magnitude for the two inequivalent Tb3+ sites in the unit cell. Overall, the collected data point to a nonmagnetic ground state in SrTb2O4 despite the presence of strong interactions.