  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.
