Neutron diffraction, muon-spin rotation, and high magnetic field investigation of the multiferroic antiferromagnetic quantum spin-chain system CuCrO₄

Multiferroic behavior in the linear-chain spin S = 1/2 compound CuCrO₄ was proposed to appear due to competing nearest- and next-nearest-neighbor exchange interactions along the chain. Here, we report on our study of the long-range magnetic ordering using powder neutron diffraction and muon-spin rotation measurements. Consistently, both methods find incommensurate long-range antiferromagnetic ordering below 8.5(3) K. We determined the magnetic structure from neutron powder diffraction patterns based on the propagation vector τ = (0, 0, 0.546(1)). At 1.9 K, the magnetic moment of Cu²⁺ was refined to 0.48(2) μ_B. The Cu moments form a helicoidal spiral with an easy plane coinciding with the equatorial planes of the Jahn-Teller elongated CuO₆ octahedra. Low-temperature high magnetic field measurements of the magnetization and the dielectric polarization show the multiferroic phase to extend up to ∼25 T, after which a new, yet unknown phase appears. Full saturation of the magnetic moment is expected to occur at fields much beyond 60 T.