# Presaturation phase with no dipolar order in a quantum ferro-antiferromagnet

## TL;DR

This study uncovers a novel quantum bond-nematic phase in BaCdVO(PO$_4$)$_2$ that appears in high magnetic fields without dipolar magnetic order, revealed through comprehensive experimental techniques.

## Contribution

It reports the discovery of a new quantum bond-nematic phase in a ferro-antiferromagnet, characterized by the absence of dipolar order and identified via multiple experimental methods.

## Key findings

- Identification of a new thermodynamic phase at high magnetic fields
- Absence of dipolar magnetic long-range order in the phase
- Evidence supporting a quantum bond-nematic state

## Abstract

Magnetization, magnetocaloric, calorimetric, neutron and X-ray diffraction and inelastic neutron scattering measurements are performed on single crystals of BaCdVO(PO$_4$)$_2$. The low-temperature crystal structure is found to be of a lower symmetry than previously assumed. The result is a more complicated model spin Hamiltonian, which we infer from measurements of the spin wave dispersion spectrum. The main finding is a novel spin state which emerges in high magnetic fields after antiferromagnetic order is terminated at $H_{c1}\simeq 4.0$ T. It is a distinct thermodynamic phase with a well-defined phase boundary at $H_{c2}\simeq 6.5$ T and is clearly separate from the fully saturated phase. Yet, it shows no conventional (dipolar) magnetic long range order. We argue that it is fully consistent with the expectations for a quantum bond-nematic state.