Pr0.5Sr0.5-xBaxMnO3: Size and Mismatch Effects on Structural and Magnetic Transitions

The structural and magnetic transitions in the Pr 0.5 Sr 0.5 - x Ba x MnO 3 series have been investigated by neutron diffraction and electron microscopy, in connection with the transport and magnetic properties, allowing a new phase diagram ( T, x, or < r A >) to be drawn. Two important points emerge from this study. First, a phase separation is observed for a large part of the diagram, described as a mixture of ferromagnetic, antiferromagnetic, and poorly ordered magnetic phases at low temperature for x > 0.2. Second, A-type antiferromagnetism (AFM) develops in nearly regular perovskite lattice. The case of Pr 0.5 Ba 0.5 MnO 3 is also discussed because its microstructure is not conventional with local cationic ordering in the random A-site matrix.