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 ${\mathrm{CuCrO}}_{4}$ 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 $\stackrel{P\vec}{\ensuremath{\tau}}=(0,0,0.546(1))$. At 1.9 K, the magnetic moment of ${\mathrm{Cu}}^{2+}$ was refined to 0.48(2) ${\ensuremath{\mu}}_{\mathrm{B}}$. The Cu moments form a helicoidal spiral with an easy plane coinciding with the equatorial planes of the Jahn-Teller elongated ${\mathrm{CuO}}_{6}$ octahedra. Low-temperature high magnetic field measurements of the magnetization and the dielectric polarization show the multiferroic phase to extend up to $\ensuremath{\sim}25$ 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.