Pre-saturation phase in the frustrated ferro-antiferromagnet Pb$_2$VO(PO$_4$)$_2$

TL;DR

This study investigates the magnetic phase diagram of Pb$_2$VO(PO$_4$)$_2$, revealing a new magnetic state near saturation characterized by complex order, using multiple experimental techniques in high magnetic fields.

Contribution

It uncovers a pre-saturation phase with complex magnetic order in a frustrated ferro-antiferromagnet, expanding understanding of magnetic phase transitions in such materials.

Findings

Discovery of a new magnetic state near saturation

Evidence of incommensurate magnetic order from NMR spectra

Identification of a discontinuous transition into this phase

Abstract

Magnetization, magnetic torque, neutron diffraction and NMR experiments are used to map out the $H$$-$$T$ phase diagram of the prototypical quasi-two-dimensional ferro-antiferromagnet Pb$_2$VO(PO$_4$)$_2$ in magnetic fields up to 27 T. When the field is applied perpendicular to the axis of magnetic anisotropy, a new magnetic state emerges through a discontinuous transition and persists in a narrow field range just below saturation. The measured NMR spectra suggest a complex and possibly incommensurate magnetic order in that regime.