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La 1-x Na x MnO 3+δ samples with well-defined cation molecularity and oxygen contents (x ) 0.05, x ) 0.13, and -0.04 e δ e 0.078) are analyzed with XRPD, electrical conductivity, static magnetization, and EPR measurements. The majority defects induced by oxygen over-and under-stoichiometry are cation and oxygen vacancies; the cation vacancies affect the magnetic properties by interrupting the interaction paths between Mn(III) and Mn(IV) ions, whereas the oxygen vacancies have a stronger influence on the structural and electrical properties and act on the magnetic properties by the overall decrease of the Mn(IV) amount and by the creation of sample regions with different magnetic features. We can state that the basic magnetic and electrical behaviors of the Na-doped lanthanum manganite compounds are driven from the Mn(IV)/Mn(III) ratio and all the peculiar behaviors are indeed caused by defects, concentration gradient and, more generally, by lattice disorder.

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