Half-Magnetization Plateau in The Kagome-Stripe-Lattice Na₂Co₃(VO₄)₂(OH)₂

Magnetization plateaus often signify quantum magnetic states arising from geometric frustration and/or quantum fluctuations. Here, we report a half-magnetization plateau in the kagome-stripe lattice (KSL) material, Na2Co3(VO4)2(OH)2. Our susceptibility measurements reveal the half-magnetization plateau under the applied field perpendicular to the quasi-one-dimensional stripe direction. To unravel the origin of the magnetization plateau, we used single crystal neutron diffraction to investigate the evolution of magnetic structures with field. At zero field, the ground state magnetic structure is a non-collinear antiferromagnetic order with reduced ordered-magnetic moments on both Co sites. Increasing the magnetic field flips the spins on one of the Co sites to ferromagnetic order, while the spins on the other Co site remain small to zero ordered-magnetic moments despite the strong magnetic field. Such robustness in reducing ordered-magnetic moments indicates strong magnetic frustration and/or quantum fluctuations in this KSL material. Furthermore, aided by the local magnetic susceptibility method using polarized neutrons, we concluded that the resulting ground state and the half-magnetization plateau are likely caused by the Dzyaloshinskii-Moriya (DM) interactions between spins on two Co sites and the strong quantum fluctuations within the 1D Co-spin chain.<br/><br/>The research was supported by the U.S. Department of Energy (DOE), Early Career Research Program Award KC0402020 and used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by ORNL.