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 tetr agonal structure with space group I4/mcm. The sample with x = 0.1 unde rgoes a transition from a paramagnetic metal to a ferromagnetic metal and then to an antiferromagnetic insulator. For x = 0.2, although it e xhibits similar magnetic transitions, resistivity in both the para-and ferromagnetic states increases with decreasing temperature. The latte r behavior is attributed to scattering of Mn : 3d conduction electrons by the localized Ce : 4f(1) moment. In the antiferromagnetic insulati ng state, the nuclear structure is determined to be orthorhombic with space group Fmmm and the magnetic structure has a layered (A)-type ant iferromagnetic spin arrangement and then, is no indication for charge ordering. (C) 1997 Elsevier Science Ltd.