STRUCTURE AND MAGNETORESISTANCE OF PR-0.7(SR0.3-YCAY)MNO3

We have investigated the structural and magnetoresitive properties for a series of Pr-0.7(Sr0.3-y)Ca-y MnO3 with y = 0 to 0.3. A systematic decrease in a- ad c-lattice parameter was observed, while b-lattice pa rameter remains as a constant with y increasing from 0 to 0.3. A signi ficant reduction in the planar Mn-O-Mn bond angle is accompanied by an enhancement of magnetoresistance. Our results can be explained based on the model of spin-disorder scattering, in which the electronic band width plays an important role on determining the relation between resi stivity and magnetization.