Structural and magnetic features of Pr, PrY, PrYDy doped and undoped CoNi nanospinel ferrites

Three distinct doped nanospinel ferrites (NSFs), Co_0.5Ni_0.5Fe₂O₄ (CN), Pr doped Co_0.5Ni_0.5Pr_xFe_2-xO₄ (CNPr); Pr and Y (PrY) doped Co_0.5Ni_0.5Pr_xY_xFe_2-2xO₄ (CNPrY); Pr, Y and Dy (PrYDy) doped Co_0.5Ni_0.5Pr_xY_xDy_xFe_2-3xO₄ (CNPrYDy) with x = 0.10, have been synthesized through hydrothermal approach. Their structural, morphological, and magnetic investigations were done via XRD, SEM with EDX, TEM and VSM. The XRD analysis confirmed both the purity of all products and cubic crystal structure of all NSFs. Their crystallite size (D_XRD) of the products was estimated between 13 and 23 nm. Utilizing the hysteresis curves (at 300 and 10 K) and temperature (T) dependence of magnetization (M), the influence of Pr, Y, and Dy dopants on the magnetic characteristics of the host material (Co_0.5Ni_0.5Fe₂O₄) is probed. It is revealed that both host and doped NSFs exhibit superparamagnetic nature at 300 K where their remanent magnetization and coercivity are negligible. The magnetization data demonstrates that incorporation of Y and Dy brings about an appreciable enhancement in the magnetization (and magnetic parameters) of host NSFs. The magnitudes of squareness ratio (SQR) for all NSFs at 10 K are noticed to be around 0.5, denoting a relatively high coercivity at this T and the generation of a single domain structure possessing uniaxial symmetry. Their field cooling (FC) modes demonstrate that as T rises, magnetization decreases slightly. Their ZFC modes display nonmonotonic decrement as T lowers. All samples exhibit a large irreversibility amongst the ZFC and FC modes, which is greatest for the CNPrYDy NSFs.