Effects of aliovalent dopants in LaMnO3: Magnetic, structural and transport properties

Abstract

In this paper, we have investigated the modification in structural, magnetic, transport, and magneto-transport properties of La0.95X0.05MnO3 polycrystalline samples prepared by the citrate combustion route with doping of different valence ions (X = Ce, Dy, Er, Sr, Na and La) as well as erbium-doped La1-xErxMnO3 samples (x = 0.0, 0.05, 0.1, and 0.3). X-ray diffraction patterns measured at room temperature confirmed the single-phase perovskite hexagonal structure with R-3c space group in all of these samples, excluding the 30% Er substituted sample. The grain sizes estimated from the SEM images were found to be in a range of 1.8–3 µm for all of the sintered samples (at 1300 °C/3h), and below 100 nm for the calcined powders (at 600 °C/3h). Curie temperatures of undoped and doped LaMnO3 powder samples were observed in the range of 230–255 K, significantly higher than the reported value (~140 K) for undoped samples. The maximum saturation magnetization (at 10 K) was obtained for the undoped sample (92 emu/g) and the largest coercivity (60 Oe) was found for the 5% Er-doped LaMnO3 sample. Temperature dependence of resistivity was measured in the absence and presence of the magnetic field (5 T), and the curves suggest a metal–insulator transition. The 5% Er-doped sample exhibited insulating behaviour while the higher Er concentration (10%) doping caused the metal–insulator transition. The rich and tuneable magnetic, transport and magneto-transport properties make these samples promising candidates for biosensors, memory devices, and other technological applications.