Microstructural, Magnetic, and Optical Properties of Pr-Doped Perovskite Manganite La 0.67Ca 0.33MnO 3 Nanoparticles Synthesized via Sol-Gel Process

摘要

We report on microstructural, magnetic, and optical properties of Pr-doped perovskite manganite (La~(1???x)Pr~(x))~(0.67)Ca~(0.33)MnO~(3)(LPCMO, x ?=?0.0–0.5) nanoparticles synthesized via sol-gel process. Structural characterizations (X-ray and electron diffraction patterns, (high resolution) TEM images) provide information regarding the phase formation and the single-crystalline nature of the LPCMO systems. X-ray and electron diffraction patterns reveal that all the LPCMO samples crystallize in perovskite crystallography with an orthorhombic structure ( Pnma space group), where the MnO~(6)octahedron is elongated along the b axis due to the Jahn-Teller effect. That is confirmed by Raman spectra. Crystallite sizes and grain sizes were calculated from XRD and TEM respectively, and the lattice fringes resolved in the high-resolution TEM images of individual LPCMO nanoparticle confirmed its single-crystalline nature. FTIR spectra identify the characteristic Mn–O bond stretching vibration mode near 600?cm_(??1), which shifts towards high wavenumbers with increasing post-annealing temperature or Pr-doping concentration, resulting in further distortion of the MnO~(6)octahedron. XPS revealed dual oxidation states of Mn_(3+)and Mn_(4+)in the LPCMO nanoparticles. UV-vis absorption spectra confirm the semiconducting nature of the LPCMO nanoparticles with optical bandgaps of 2.55–2.71?eV. Magnetic measurements as a function of temperature and magnetic field at field cooling and zero-field cooling modes, provided a Curie temperature around 230?K, saturation magnetization of about 81?emu/g, and coercive field of 390?Oe at 10?K. Such magnetic properties and the semiconducting nature of the LPCMO nanoparticles will make them as suitable candidate for magnetic semiconductor spintronics.