Phase diagram of the La1-xCaxMnO3 compound (0.5≤x≤0.9) -: art. no. 134414

We have studied the phase diagram of La1-xCaxMnO3 for 0.5less than or equal toxless than or equal to0.9 using neutron powder diffraction and magnetization measurements. At 300 K all samples are paramagnetic and single phase with crystallographic symmetry Pnma. As the temperature is reduced a structural transition is observed which is to a charge-ordered state only for certain x. On further cooling the material passes to an antiferromagnetic ground state with Neel temperature T-N that depends on x. For 0.8less than or equal toxless than or equal to0.9 the structural transformation occurs at the same temperature as the magnetic transition. Overall, the neutron-diffraction patterns were explained by considering four phase boundaries for which La1-xCaxMnO3 forms a distinct phase: the charge-ordered phases at x=0.5 and x=2/3, the monoclinic and C-type magnetic structure at x=0.80-0.85, and the G-type magnetic structure at x=1. Between these phase boundaries the magnetic reflections suggest the existence of mixed compounds containing both phases of the adjacent phase boundaries.