Independent Freezing of Charge and Spin Dynamics inLa1.5Sr0.5CoO4

We present elastic and quasielastic neutron scattering measurements characterizing peculiar short-range charge-orbital and spin order in the layered perovskite material La{sub 1.5}Sr {sub 0.5}CoO {sub 4} . We find that below T{sub c}{approx}750 K holes introduced by Sr doping lose mobility and enter a statically ordered charge glass phase with loosely correlated checkerboard arrangement of empty and occupied d{sub 3z{sup 2}-r{sup 2}} orbitals (Co{sup 3+} and Co{sup 2+} ). The dynamics of the resultant mixed spin system is governed by the anisotropic nature of the crystal-field Hamiltonian and the peculiar exchange pattern produced by the orbital order. It undergoes a spin freezing transition at a much lower temperature, T{sub s}{approx}