  Y0.5Ca0.5BaCo4O7 was recently introduced as a possible candidate for
capturing some of the predicted classical spin kagome ground state features.
Stimulated by this conjecture we have taken up a more complete study of the
spin correlations in this compound with neutron scattering methods on a powder
sample characterized with high-resolution neutron diffraction and the
temperature dependence of magnetic susceptibility and specific heat. We have
found that the frustrated near neighbor magnetic correlations involve not only
the kagome planes but concern the full Co sub-lattice as evidenced by the
analysis of the wavevector-dependence of the short range order. We conclude
from our results that the magnetic moments are located on the Co sub-lattice as
a whole and that correlations extend beyond the two-dimensional kagome planes.
We identify intriguing dynamical properties, observing high-frequency
fluctuations with a lorentzian line-width {\Gamma} <= 20 meV at ambient
temperature. On cooling a low-frequency (~ 1 meV) dynamical component develops
alongside the high-frequency fluctuations, which eventually becomes static at
temperatures below T ~ 50 K. The high-frequency response with an overall
line-width of ~ 10 meV prevails at T <= 2 K coincident with a fully elastic
short-range ordered contribution.
