Evolution of Magnetotransport Properties and Spin-Glass Behavior of the La_0.7-xNd_xPb_0.3MnO₃ System

Abstract

The effect of neodymium substitution on the lanthanum site in La 0.7- x Nd x Pb 0.3 MnO 3 perovskite polycrystalline has been systematically studied. The substitution of neodymium for lanthanum causes structure change from rhombohedral to orthorhombic. Ferromagnetism is suppressed as neodymium content increases. 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-paramagnetic transition temperature values are lower for the neodymium phases than for the lanthanum ones. Therefore, the introduction of neodymium degrades symmetry of the structure, diminishes the spin-coupling exchange interaction, 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.