High field magnetisation of the frustrated one dimensional quantum antiferromagnet LiCuVO4

TL;DR

This study explores the high field magnetisation behavior of the frustrated 1D quantum antiferromagnet LiCuVO4, revealing a phase transition and challenging previous theoretical predictions about its magnetic singularities.

Contribution

It provides the first experimental evidence of a middle field cusp singularity in LiCuVO4 and compares it with numerical DMRG results, clarifying the nature of its magnetic phase transitions.

Findings

An anomaly at ~7.5 T in magnetisation derivative indicates a phase change.

Numerical DMRG shows no MFCS in the parameter range of LiCuVO4.

The anomaly is due to a change from a helix to another spin structure.

Abstract

We have investigated the high field magnetisation of the frustrated one dimensional compound LiCuVO4. In zero field, LiCuVO4 undergoes long range antiferromagnetic order at T_{N} ~ 2.5 K with a broad short range Schottky type anomaly due to one dimensional correlations in the specific heat at 32 K. Application of a magnetic field induces a rich phase diagram. An anomaly in the derivative of the magnetisation with respect to the applied magnetic field is seen at ~ 7.5 T with H ll c in the long range order phase. We investigated this in terms of a first experimental evidence of a middle field cusp singularity (MFCS). Our numerical DMRG results show that in the parameter range of LiCuVO4 as deduced by inelastic neutron scattering (INS), there exists no MFCS. The anomaly in the derivative of the magnetisation at ~ 7.5 T is therfore assigned to a change in the spin structure from the ab plane helix seen in zero field neutron diffraction.