Structural and Magnetic Properties of La2/3D1/3MnO3 (D = Ca, Sr, Ba) Manganites Prepared By Ball Milling

Abstract

In this research, we report on the synthesis and characterization of La_0.67Ca_0.33MnO₃ (LCMO), La_0.67Ba_0.33MnO₃ (LBMO), and La_0.67Sr_0.33MnO₃ (LSMO) perovskites. Precursor powders for the perovskite samples were prepared using ball mailing technique. The resulting powder was pressed into disks which were subsequently sintered at 1000º C for 2h. The structural characteristics of the prepared samples were investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM), and the magnetic properties were investigated using vibrating sample magnetometry (VSM). XRD pattern of LCMO sample revealed a pure perovskite phase with Pnma space group, while the pattern of LSMO sample revealed a pure perovskite with  space group. XRD pattern of LBMO sample, however, demonstrated the presence of a major perovskite phase with  symmetry, together with a secondary BaMnO₃ phase. This secondary phase disappeared upon sintering LBMO at a higher temperature of 1100º C. Isothermal magnetic measurements and thermomagnetic curves revealed that LCMO was paramagnetic at room temperature. However, LSMO exhibited soft ferromagnetic behavior at room temperature, with T_c = 380 K and M_s = 50.9 emu/g. Also, LBMO sample sintered at 1000º C exhibited soft ferromagnetic behavior at room temperature, with Curie temperature T_c = 343 K and a rather low saturation magnetization of M_s = 30.7 emu/g. The higher sintering temperature of LBMO compound resulted in a significant increase of the saturation magnetization to 50.8 emu/g for the sample sintered at 1100º C.  

Keywords: Perovskites, Structural properties, Magnetic properties, Thermomagnetic curves.