Presaturation phase in the frustrated ferro-antiferromagnet Pb2VO(PO4)2

Magnetization, magnetic torque, neutron diffraction and NMR experiments are used to map out the $H\ensuremath{-}T$ phase diagram of the prototypical quasi-two-dimensional ferro-antiferromagnet ${\mathrm{Pb}}₂\mathrm{VO}{({\mathrm{PO}}₄)}₂$ in magnetic fields up to 27 T. When the field is applied perpendicularly 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.