Effect of rare-earth-site cations on the physical properties ofLa0.7−yNdyPb0.3MnO3single crystals

Abstract

Single crystals of $La_{0.7–-y}Nd_yPb_{0.3}MnO_3$ with different y are grown by flux growth technique. The influence of change in average cationic radius $(\langle r_A\rangle)$ and cation size disorder $(\sigma^2)$ on the transport and magnetic properties of these crystals due to the presence of different cations (La and Nd) on the rare-earth sRd site is studied. Curie temperature $T_C$ and metal-insulator transition temperature $T_M_I$ are sensitive to the R site occupation. The temperature dependence of magnetization of $La_{0.7}Nd_yPb_{0.3}MnO_3$ is consistent with spin wave excitations according to the Bloch $T^{3/2}$ law at zero magnetic field limit. The Nd-based systems follow $T^{3/2}$ law only in a certain range of temperature and deviate at low temperatures, which is ascribed to a probably canted ordering of Nd and Mn moments with an antiferromagnetic component at very low temperatures. The values of spin stiffness constants and saturation magnetization vary systematically with changing occupation on the R site. Specific heat measurements of Nd containing samples show a Schottky-like anomaly at low temperature (below 15 K), which increases with the concentration of Nd ions in the lattice. It is concluded that the magnetic properties of manganites with Nd are affected by a tendency for magnetic ordering of the Nd ions.