The Pr0.50Sr0.50CoO3 perovskite exhibits unique magnetostructural properties among the rest of ferromagnetic (FM)/metallic Ln0.50Sr0.50CoO3 compounds. The sudden orthorhombic-tetragonal (Imma → I4/mcm) structural transition produces an unusual magnetic behavior vs temperature and external magnetic fields. The symmetry change is responsible for a spontaneous spin rotation in this metallic oxide.
We have studied half-doped Ln0.50 (Sr1−xAx )0.50CoO3 cobaltites varying the ionic radius rA of A-site cations (divalent cations and lanthanides) to complete the T-rA phase diagram. The influence of the structural distortion and the A-cation size for the occurrence of a spontaneous spin reorientation in the metallic state has been investigated. As the magnetization reorientation is driven by the temperature-induced collapse of the orthorhombic distortion, a careful investigation of the structural symmetry is presented, varying the structural distortion of the Sr-rich half-doped cobaltites by means of both compositional and temperature changes. The region in the phase diagram of these FM/metallic cobaltites where Fm m m magnetic symmetry replaces Im m a was determined. In that region, the magnetization direction has rotated 45 ° within the a-b plane from the former to the latter.