Magnetic Correlations in the Extended KagomeYBaCo4O7Probed by Single-Crystal Neutron Scattering

Abstract

We have studied the frustrated system ${\mathrm{YBaCo}}_4{\mathrm{O}}_{7.0}$ generally described as an alternating stacking of kagome and triangular layers of magnetic ions on a trigonal lattice, by single-crystal neutron diffraction experiments above the Néel ordering transition. Experimental data reveal pronounced magnetic diffuse scattering, which is successfully modeled by direct Monte Carlo simulations. Long-range magnetic correlations are found along the $c$ axis, due to the presence of corner-sharing bipyramids, creating quasi–one-dimensional order at finite temperature. In contrast, in the kagome layers ($ab$ plane), the spin-spin correlation function, displaying a short-range 120° configuration, decays rapidly as typically found in spin liquids. ${\mathrm{YBaCo}}_4{\mathrm{O}}_7$ experimentally realizes a new class of two-dimensional frustrated systems where the strong out-of-plane coupling does not lift the in-plane degeneracy, but instead acts as an external “field.”