Nuclear and magnetic structures in new distorted perovskites Pr0.5-xCexSr0.5MnO3 (x = 0.1 and 0.2)

Neutron diffraction, magnetic susceptibility and electrical transport measurements have been carried out on Pr0.5-xCexSr0.5MnO3 with x = 0.1 and 0.2. At room temperature, these two samples crystallize in a tetragonal structure with space group I4/mcm. The sample with x = 0.1 undergoes a transition from a paramagnetic metal to a ferromagnetic metal and then to an antiferromagnetic insulator. For x = 0.2, although it exhibits similar magnetic transitions, resistivity in both the para-and ferromagnetic states increases with decreasing temperature. The latter behavior is attributed to scattering of Mn : 3d conduction electrons by the localized Ce : 4f(1) moment. In the antiferromagnetic insulating state, the nuclear structure is determined to be orthorhombic with space group Fmmm and the magnetic structure has a layered (A)-type antiferromagnetic spin arrangement and then, is no indication for charge ordering. (C) 1997 Elsevier Science Ltd.