  We present a scheme to generate steady-state atomic spin squeezing in a
cavity QED system using cavity-mediated Raman transitions to engineer effective
atom-photon interactions, which include both linear and nonlinear (dispersive)
atom-cavity couplings, on a potentially equal footing. We focus on a regime
where the dispersive coupling is very large and find that the steady state of
the system can in fact be a strongly spin-squeezed Dicke state,
$|N/2,0\rangle$, of the atomic ensemble. These states offer Heisenberg-limited
metrological properties and feature genuine multipartite entanglement among the
entire atomic ensemble.
