High-pressure inelastic neutron scattering study of the anisotropic $S=1$ spin chain [Ni(HF$_2$)(3-Clpyradine)$_4$]BF$_4$

TL;DR

This study investigates how applying hydrostatic pressure affects the magnetic properties of a one-dimensional $S=1$ spin chain material, revealing an increase in anisotropy that pushes the system deeper into the large-$D$ quantum paramagnetic phase.

Contribution

The paper extends previous neutron scattering experiments to high pressure, demonstrating how pressure influences the anisotropy ratio $D/J$ in the spin chain material.

Findings

Pressure increases $D/J$ from 1.5 to 3.2.

System moves further into the large-$D$ phase with pressure.

Neutron scattering and DMRG calculations agree on anisotropy change.

Abstract

[Ni(HF$_2$)(3-Clpyradine)$_4$]BF$_4$ (NBCT) is a one-dimensional (1-D), $S=1$ spin chain material that shows no long-range magnetic order down to thermometer temperatures of 0.1 K. Previous ambient pressure inelastic neutron scattering experiments identified NBCT to be in the large-$D$ quantum paramagnetic phase of the $D/J$ phase diagram, where $D$ is the axial single-ion anisotropy and $J$ is the intrachain superexchange. Here, we extend the previous experiments to be at a hydrostatic pressure of 0.9 GPa. By comparing to density matrix renormalization group calculations, we find $D/J$ increases from 1.5 to 3.2 as pressure increases from 0 GPa to 0.9 GPa, which pushes the system further into the large-$D$ phase.