Magnetic ground state of the frustrated spin-1/2 chain compound beta-TeVO4 at high magnetic fields

Frustrated spin-1/2 chains, despite the apparent simplicity, exhibit a remarkably rich phase diagram comprising vector-chiral (VC), spin-density-wave (SDW), and multipolar/spin-nematic phases as a function of the magnetic field. Here we report a study of beta-TeVO4, an archetype of such compounds, based on magnetization and neutron diffraction measurements up to 25 T. We find the transition from the helical VC ground state to the SDW state at similar to 3 T for the magnetic field along the a and c crystal axes, and at similar to 9 T for the field along the b axis. The high-field (HF) state, existing above similar to 18 T, i.e., above similar to 1/2 of the saturated magnetization, is an incommensurate magnetically ordered state and not the spin-nematic state, as theoretically predicted for the isotropic frustrated spin-1/2 chain. The HF state is likely driven by sizable interchain interactions and symmetric intrachain anisotropies uncovered in previous studies. Consequently, the potential existence of the spin-nematic phase in beta-TeVO4 is limited to a narrow field range, i.e., a few tenths of a tesla bellow the saturation of the magnetization, as also found in other frustrated spin-1/2 chain compounds.