The effect of oxygen content on the magnetic and transport properties of the ferromagnetic Eu0.9Ca0.1BaCo2O5.5+{delta} has been carried out. Unlike the increase in TC with calcium content, paradoxally the TC value decreases with the increase in oxygen (Co4+) content as observed in the undoped phase. This result unveils the hidden generic magnetic feature of the LnBaCo2O5.5 system in the calcium doped phase. This behaviour supports strongly the appearance of Co3+ disproportion action into Co4+ and Co2+ and the magnetic phase separation scenario of ferromagnetic domains embedded in an antiferromagnetic matrix. All the samples covering a wide range of oxygen content, exhibit a p-type conductivity.
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