MAGNETIC-ORDERING AND RELATION TO THE METAL-INSULATOR-TRANSITION IN PR1-XSRXMNO3 AND ND1-XSRXMNO3 WITH X-SIMILAR-TO-1 2/

We studied three distorted perovskite manganites, Pr1/2Sr1/2MnO3 and N d1-xSrxMnO3 with x = 1/2 and 0.55 by the neutron diffraction technique . Two samples with x = 1/2 exhibit a transition from a ferromagnetic ( FM) metal to an antiferromagnetic (AFM) nonmetal. We demonstrate that, in the low temperature phase, Nd1/2Sr1/2MnO3 has a CE-type AFM struct ure with charge ordering, while Pr1/2Sr1/2MnO3 and Nd0.45Sr0.55MnO3 ex hibit an A-type layered AFM structure, but show no clear sign of charg e ordering. From the present results, we suggest a possible anisotropy of transport as well as magnetic properties in the A-type AFM structu re near x similar to 1/2.