Local structure and magnetic properties of Mn3+-O-Fe3+ superexchange interaction in an oxygen-vacant perovskite: Experimental and theoretical study

In this work we report an experimental and theoretical study on the local structure and magnetic properties of Mn3+-O-Fe3+ superexchange interaction for an oxygen-vacant perovskite PrBaMnFeO5+δ with δ ∼ 0.5. Structural studies were performed by high resolution X-Ray diffraction technique in normal and anomalous scattering, modeled using an orthorhombic biphasic system corresponding to an oxygen-rich and oxygen-poor stoichiometries. Mössbauer spectroscopy showed the presence of two orthorhombic iron sites, one ascribed to a fully octahedral coordination and another, highly distorted, ascribed to a pyramidal coordination, in full agreement with theoretical DFT + U + SO calculations. The samples showed a spin-glass transition at ∼20 K and mainly the presence of Mn3+-O-Fe3+ type-G antiferromagnetic superexchange interactions. However, our theoretical calculations using first principles also suggested that the presence of oxygen vacancies in certain conditions could be possibly promoting local ferromagnetic interactions.