Magnetic structure and domain conversion of the quasi-2D frustrated antiferromagnet CuCrO2 probed by NMR

Abstract

We have carried out 63,65 Cu NMR spectra measurements in a magnetic field up to about 15.5 T on a single crystal of the multiferroic triangular lattice antiferromagnet CuCrO 2 . The measure ments were performed for perpendicular and parallel orientations of the magnetic field with respect to the c axis of the crystal, and the detailed angle dependence of the spectra on the magnetic field direction in the ab plane was studied. The shape of the spectra can be well described in the model of spiral spin structure proposed by recent neutron diffraction experiments. When the field is rotated perpendicular to the crystal c axis, we observed, directly for the first time, a remarkable reorientation of the spin plane simultaneous with rotation of the incommensurate wavevector, by quantitatively deducing the conver sion of the energetically less favorable domain to a more favorable one. At high enough fields parallel to the c axis, the data are consistent with either a field induced commensurate spiral magnetic structure or an incommensurate spiral magnetic structure with a disorder in the c direction, suggesting that high fields may have influence on interplanar ordering.

Search for a nematic phase in the quasi-two-dimensional antiferromagnet CuCrO2 by NMR in an electric field

“…As elaborated in Refs. [3,4] the "double-horn" and "helmet" shaped NMR spectra in CuCrO 2 are specific for incommensurate magnetic structures within triangular planes with inter-plane order and disorder, respectively. We emphasize that the high-field helmet shaped spectra persists up to 45 T (Ref.…”

“…According to Refs. [3,[9][10][11][12], the application of external electric field E along [110] favors the three domains with positive projections of n E , while the application of external magnetic field along [110] favors the two domains with n collinear to H. This scheme allows control over the domain arrangement of a sample. For magnetic field H c, i.e.…”

“…A single crystal of CuCrO 2 was grown by the method described in our previous work. 3 The crystal was cut into a thin plate with dimensions 2.4 × 1.5 × 0.7 mm 3 . Silver epoxy was painted on the widest end faces and served as the electrodes.…”

“…[2]. In recent Cu NMR investigations 3,4 the hysteretic behaviour of spectral shapes in the field range 14-45 T which is much below the fields of exchange scale (µ 0 H sat ≈ 280 T) was observed. The field evolution of NMR spectra was explained by a loss of usual interplanar ordering in the high field range.…”

Multiferroicity of CuCrO2 tested by electron spin resonance

“…Results of the magnetization, electric polarization and ESR and NMR experiments 7,15,16 have been discussed within the framework of the planar spiral spin structure at fields studied experimentally: µ 0 H < 14 T ≪ µ 0 H sat (µ 0 H sat ≈ 280 T). The orientation of the spin plane is determined by the biaxial crystal anisotropy and the applied magnetic and electric fields.…”