Strontium doping as a means of influencing the characteristics of neodymium orthoferrite nanocrystals synthesized by co-precipitation method

Orthoferrite Nd_1−xSr_xFeO₃ nanocrystals with the size 30–50 nm have been successfully synthesized via a simple co-precipitation method through the hydrolysis of Nd(III), Sr(II), and Fe(III) cations in boiling water with 5% Na₂CO₃ solution as a precipitating agent and subsequent annealing at various temperatures (700, 850, and 950 °C) for 60 min. Introduction of Sr²⁺ cations to the nominal value x = 0.2 into the NdFeO₃ lattice led to an increase in the average crystal size for all annealing temperatures. Synthesized Nd_1−xSr_xFeO₃ (x = 0, 0.1) samples are soft magnetic materials with low coercivity (H_c) and remanent magnetization (M_r), and Nd_1−xSr_xFeO₃ (x = 0.2, 0.3) are hard magnetic materials with very high values of the H_c and M_r. The H_c and M_r of the Nd_0.76Sr_0.18FeO_3.52 sample were higher than those of NdFe_1.11O_3.36 by 33.3 and 70.9 times, respectively. Synthesized Nd_1−xSr_xFeO₃ nanopowders with x = 0 and 0.1 can be applied in the production of the cores of transformers, electromagnets, and conductors; and those with x = 0.2 and 0.3 can be used for permanent magnets or magnetic recording on hard disks and tapes.