Synthesis and Magnetic Characterization of La_(2-x)Sr_xCuO_4 Nanoparticles

摘要

Non-doped and strontium-doped lanthanum cuprates (La_2CuO_4 (LCO) and La_(1.85)Sr_(0.15)CuO_4 (LSCO15)) in nano-sized particles were synthesized by the chemically dissolved technique employing HNO_3 as the dissolving agent. The structural and magnetic properties were investigated by using an x-ray diffraction (XRD) apparatus and a superconducting quantum interference device (SQUID) magnetometer, respectively. The XRD patterns of LCO and LSCO15 show the formation of the single phase without impurities after the calcinations in air at 1100oC for 15 h and the post-annealing in oxygen at 800 oC for 24 h. The average crystallite sizes of LCO and LSCO15 samples were in a range of around 100 nm confirming nano-sized particles. The LCO and LSCO15 nanoparticles exhibit superconductivity at the superconducting (SC) transition temperature, Tc, of 23 K and 38 K, respectively. The magnetization curve measurements have revealed that both samples show the appearance of ferro- and dia-magnetic behavior at room temperature and the appearance of superconductivity at low temperatures. This result may indicate the coexistence of ferromagnetism and superconductivity below Tc in the nano-sized cuprates.