Structure, charge ordering, and magnetic properties of perovskite Sm0.5Ca0.5MnO3 manganite

Half-doped perovskite Manganese oxide has been widely studied because of its excellent properties such as colossal magnetoresistance (CMR) effect and charge-ordered (CO) phase separation. In this work, four Sm_0.5Ca_0.5MnO₃ samples with different particle sizes are prepared by high-temperature solid-state reaction and ball milling. The crystal structure of the samples is studied by X-ray diffraction (XRD). The Sm_0.5Ca_0.5MnO₃ sample is single phase, which belongs to orthorhombic structure. The surface morphology and particle size of the samples are examined by scanning electron microscope (SEM). The average particle size of the sample without ball milling is about 4 μm. With ball milling time for 12 h, 24 h, and 36 h, the particle size decreases, and finally it reaches hundreds to tens of nanometers. This shows that ball milling is an effective way to control the particle size. The M–T curves and M–H hysteresis loops of the samples are measured by physical properties measurements systems (PPMS). The two M–T curves measured in the warming and cooling processes do not overlap for Sm_0.5Ca_0.5MnO₃ without ball milling, and the phenomenon of thermal hysteresis appears. Meanwhile, the M–T curve has a significant protuberance peak near 270 K. All of these indicate the CO behavior, whereas the particle size of Sm_0.5Ca_0.5MnO₃ decreases with different milling times (12–36 h) and the CO phase is suppressed gradually, which leads to the decrease of CO temperature, magnetization, remanence, and coercivity.