Evolution of magnetic properties and canted spin behavior of the La/sub 0.7-x/Pr/sub x/Pb/sub 0.3/MnO/sub 3/ manganite

Summary form only given. The colossal magnetoresistance (CMR) materials have attracted considerable attention recently. In this report, the results of detailed investigation of the structural and magnetic properties of the La/sub 0.7-x/Pr/sub x/Pb/sub 0.3/MnO/sub 3/ (0 /spl les/ /spl times/ /spl les/ 0.7) over a wide range of compositions are presented and compared with the consequences deduced from classical magnetic mechanism in this article. The regular replacement of smaller Pr ion in the La site causes structure change from rhombohedral symmetry with space group R3~c to orthorhombic structure. Therefore, the introduction of praseodymium enhances the distortion of the perovskite, diminishes the spin-coupling exchange interaction, and decreases the ferromagnetic-paramagnetic transition temperature values from 332 K for x = 0 to 163 K for x = 0.7. For Pr-rich manganites, due to the canted spin of magnetic Pr ions, the magnetizations are hardly saturated under low field and the saturated moment are larger than that of the La-rich manganites under high field. The curves taken from FC-ZFC measurement indicated that the magnetic order changes from a ferromagnetic long-range order with x = 0.0 to a spin-glass nature with x = 0.7. These of regular substitution are in good agreement with increasing the B value in Bloch´s T/sup 3/2/ law, M(T)=Ms(0)(1-BT/sup 3/2/), decreasing the spin-wave stiffness parameter D in quadratic dispersion relation, E/sub k/ = Dk/sup 2/ and reducing the exchange energy E/sub k/, as well as resulting in the lower value of Tc.