Effect of annealing temperature and cadmium doping on structure and magnetic properties of neodymium orthoferrite nanoparticles synthesized by a simple co-precipitation method

A series of Nd_1-xCd_xFeO₃ (x = 0.1, 0.2 and 0.3) nanoparticles were successfully synthesized from Nd(III), Cd(II) and Fe(III) nitrates by a simple co-precipitation method in boiling water with a 5% sodium hydroxide aqueous solution (without any surfactants) and annealed at 700, 850 and 950 °C for 1 h. SEM and TEM analyses showed particle sizes in the range of 50–70 nm. According to XRD the average crystallite size increased with the annealing temperature, but decreased when the cadmium concentration increased. As the annealing temperature was raised from 700 to 950 °C, the magnetic properties, such as coercivity (H_c), remanent magnetization (M_r) and saturation magnetization (M_s), of the Nd_0.8Cd_0.2FeO₃ sample also increased. In general, the H_c, M_r and M_s values increased with the degree of cadmium doping. The synthesized Nd_1-xCd_xFeO₃ nanopowders have much larger coercivity values than some other rare-earth perovskites, such as Nd_1-xSr_xFeO₃, NdFe_1-xCo_xO₃, LaFe_1-xTi_xO₃, YFe_1-xNi_xO₃, Y_1-xCd_xFeO₃, La_1-xCd_xFeO₃ or Bi_1-xCd_xFeO₃. The high H_c value (1916.52–4833.41 Oe) of the synthesized Nd_1-xCd_xFeO₃ nanopowders enables their use for permanent magnets or magnetic recording on hard disks and tapes.