Spin configurations in the frustrated spin system YBaCo$_{4}$O$_{7}$ by $^{59}$Co NMR*

The frustrated spin system YBaCo$_{4}$O$_{7}$ has both kagom\'{e} and triangular planes of cobalt ions alternating with each other. The cobalt spins in the triangular layers order antiferromagnetically below the N\'{e}el temperature at 106 K. The configurations of the cobalt spins have been studied by both neutron scattering\footnote{D. D. Khalyavin, P. Manuel, J. F. Mitchell, and L. C. Chapon, Phys Rev B \textbf{82,} 094401 (2010).} and zero applied field $^{59}$Co NMR. While the triangular spin orientations are in agreement for the two approaches, this is not the case for the kagom\'{e} layers. The present in-field sample rotation NMR experiments confirm our previous finding that the triangular spins are aligned perpendicular to the [110] crystallographic direction and provide strong evidence that the spins in the kagom\'{e} layers are orthogonal those in the triangular layers in what may be described as an internal-field-induced spin-flop configuration.