Local lattice distortions and electronic phases in perovskite manganite Pr0.5Sr0.5MnO3

Abstract

We use variable temperature and magnetic field total x-ray scattering to study the crystal structure of the strongly correlated Pr _0.5 Sr _0.5 MnO _3 perovskite, which is a paramagnetic insulator at room temperature, becomes a ferromagnetic metal at 272 K and, upon further decreasing the temperature, turns into an antiferromagnetic insulator at 105 K. We find that a model featuring a monoclinic symmetry captures the structure and its temperature and field evolution well, eliminating the need to evoke a phase segregation scenario as done in prior studies. It appears that coupled variations in Mn–oxygen bonding distances and angles from their values in an undistorted perovskite lattice, i.e., coupled local lattice distortions, assist the phase transitions in Pr _0.5 Sr _0.5 MnO _3 , contributing to its unique physical properties. Local structural distortions thus emerge as an important degree of freedom in strongly correlated systems, in particular perovskite manganates, and, therefore, they should be fully accounted for when their fascinating physics is considered.

Keywords

• local structure
• lattice instability
• phase transitions
• manganates
• charge and orbital ordering