Effects of Pr3+ ion doping on magnetic features of Ni–Co nanospinel ferrites synthesized via sonochemical approach

Abstract

The praseodymium ion (Pr3+) substituted Ni0.5Co0.5Fe2O4 nanospinel ferrites, (Co0.5Ni0.5PrxFe2-xO4 (Pr → CoNi) (x ≤ 0.10) NSFs), were synthesized via sonochemical route. XRD confirmed the single cubic structure of all samples with the crystallite size within the range of 9–11 nm.The morphology of (Pr → CoNi) (x ≤ 0.10) NSFs) particles was analyzed by SEM and TEM and showed the spherical shape. Mossbauer study showed that the larger Pr3+ ions prefer the B site. According to the magnetic study, the superparamagnetic character increased with increase of Pr3+ions. The magnetic characteristics are elucidated through both hysteresis curves and temperature (T) dependence of magnetization (M). Magnetization (M) vs external field (H) hysteresis curves were performed at both 300 (RT) and 10 K. It is revealed that Pr → CoNi NSFs exhibit superparamagnetic (SPM) nature performed at RT. Saturation magnetization (Ms), magnetic moment (nB), squareness ratio (SQR), remanence (Mr), and coercivity (Hc) were determined. The Hc of Pr → CoNi (x ≤ 0.10) NSFs was found to be larger than that of the host material. On the other hand, at both temperatures, the magnetization data demonstrates the crucial impact of Pr3+ ions which diminish the Ms, Mr and nB of the host material. The magnetic parameters for Pr → CoNi (x ≤ 0.10) NSFs barely fluctuate and depend on the cation distribution. At 10 K, the SQR of all samples is calculated to be ∼ 0.5 which reflects the uniaxial symmetry and a single-domain structure formation. For Pr → CoNi (x ≤ 0.10) NSFs, much lower SQR values are attained at room temperature (RT), indicating a decrease in the exchange interaction, and suggesting a multi-domain wall structure. For Pr → CoNi (x ≤ 0.10) NSFs, the M values through field-cooling (FC) curves exhibit a slight decrease with increasing T. Their zero field-cooling (ZFC) curves display a nonmonotonic decrease with the decreasing T and result in a low magnetization at low Ts. ZFC and FC curves of Pr → CoNi (x ≤ 0.10) NSFs indicate a large irreversibility.