Magnetic phases of the quasi-two-dimensional antiferromagnetCuCrO2on a triangular lattice

We have carried out $^63,65\mathrm{Cu}$ NMR spectra measurements in a magnetic field up to about 45 T on a single crystal of a multiferroic triangular antiferromagnet ${\mathrm{CuCrO}}₂$. The measurements were performed for magnetic fields aligned along the crystal $c$ axis. Field and temperature evolution of the spectral shape demonstrates a number of phase transitions. It was found that the 3D magnetic ordering takes place in the low field range ($H\ensuremath{\lesssim}15$ T). At higher fields magnetic structures form within individual triangular planes whereas the spin directions of the magnetic ions from neighboring planes are not correlated. It is established that the 2D-3D transition is hysteretic in field and temperature. Line-shape analysis reveals several possible magnetic structures existing within individual planes for different phases of ${\mathrm{CuCrO}}₂$. Within certain regions on the magnetic $H\ensuremath{-}T$ phase diagram of ${\mathrm{CuCrO}}₂$ a 3D magnetic ordering with tensor order parameter is expected.