The realization of oxygen over stoichiometry through oxidation of Co2+ into Co3+ in the 2H-perovskite related oxides Sr1+x(Mn1-xCox)O3 is demonstrated, leading to a large family of cation deficient Ising chain...

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The spin chain oxide Ba 4 CoPt 2 O 9+Δ gathers several features that make it close to a 1D Ising S = 1/2 system: (i) it contains only one type of spins, which are associated to a Kramers doublet with a substantial gap from the first excited state; (ii) these spins exhibit a pronounced uniaxial anisotropy; (iii) their easy-axis is perfectly oriented along the spin chain direction; (iv) the spin chains remain uncoupled down to at least 2 K. It is reported that the magnetic susceptibility, the isothermal magnetization and the specific heat in fields up to 9 T can be well accounted for by the theoretical predictions for 1D Ising S = 1/2 systems, yielding consistent set of values for the Landé factors and the intrachain coupling. The presence of missing spins associated to the oxygen overstoichiometry is taken into account, as well as the polycrystalline nature of the samples which requires to consider angular averages of the anisotropic physical properties.