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Magnetostructural coupling, magnetic ordering and cobalt spin reorientation in metallic Pr0.50Sr0.50CoO3 cobaltite

In half-doped Pr0.50A0.50CoO3 metallic perovskites, the spin-lattice coupling brings about distinct magnetostructural transitions for A=Ca and A=Sr at temperatures close to 100 K. However, the ground magnetic properties of Pr0.50Sr0.50CoO3 (PSCO) strongly differ from Pr0.50Ca0.50CoO3 ones, where a partial Pr3+ to Pr4+ valence shift and Co spin transition makes the system insulating below the transition. This work investigates and describes the relationship between the Imma-to-I4/mcm symmetry change [Padilla-Pantoja et al, Inorg. Chem. 53, 12297 (2014)] and the original magnetic behavior of PSCO versus temperature and external magnetic fields. The FM1 and FM2 ferromagnetic phases, above and below the magnetostructural transition (TS1=120 K) have been investigated. The FM2 phase of PSCO is composed of [100] FM domains, with magnetic symmetry Im'm'a (mz=0). The magnetic space group of the FM1 phase is Fm'm'm (with mx=my). Neutron data analyses in combination with magnetometry and earlier reports results agrees with a reorientation of the magnetization axis by 45 deg within the a-b plane across the transition, in which the system retains its metallic character. The presence below TS1 of conjugated magnetic domains, both of Fm'm'm symmetry but having perpendicular spin orientations along the diagonals in the xy-plane of the tetragonal unit cell, is at the origin of the anomalies observed in the macroscopic magnetization. A relatively small field m0H > 30 mT is able to reorient the magnetization within the a-b plane, whereas a higher field (m0H,[H//z] >1.2 T at 2K) is necessary to align the Co moments perpendicular to a-b plane. Such a spin reorientation, in which the orbital and spin components of the Co moment rotate joined by 45deg, was not observed with other lanthanides different to praseodymium.