Evolution of magnetotransport properties and spin-glass behavior of the La0.7-xNdxPb0.3MnO3 system

The effect of neodymium substitution on the lanthanum site in La0.7-xNdxPb0 .3MnO3 perovskite polycrystalline has been systematically studied. The subs titution of neodymium for lanthanum causes structure change from rhombohedr al to orthorhombic. Ferromagnetism is suppressed as neodymium content incre ases. The magnetic order changes from a ferromagnetic long-range order with x = 0.0 to a spin-glass nature with x = 0.7. Besides. the ferromagnetic-pa ramagnetic transition temperature values are lower for the neodymium phases than for the lanthanum ones. Therefore. the introduction of neodymium degr ades symmetry of the structure, diminishes the spin-coupling exchange inter action. and results in changes of magnetic properties. This fact is in good agreement with increasing the B value in Bloch's T-3/2 law and decreasing the spin-wave stiffness parameter D in quadratic dispersion relation.