Magnetic, structural, and morphological properties behavior of Ni1–xCoxFe2O4 magnetic nanoparticles: Theoretical and experimental study

Abstract

In this work, we synthesized nanoparticles of the Ni1-xCoxFe2O4 (with x = 0.25, 0.50, and 0.75) inverse spinel by the hydrothermal method. Scanning transmission electron microscopy (STEM) analysis and elemental characterization revealed the formation of nanoparticles of the order of ∼3 nm with a homogeneous distribution of their constituents, denoting the correct material synthesis. The results show that as the content of Co2+ increases, the cell parameter of the structures increases and the crystallite size increases. Besides, the magnetic characterization exhibits an increase in the saturation magnetization as the Co2+ content moves from x = 0.25 to x = 0.75, on the other hand, the coercive field decreases, which is attributed to the superparamagnetic behavior of the structures. By Density Functional Theory (DFT) calculation demonstrates that the inverse spinel is the most favorable configuration for both NiFe2O4 and CoFe2O4 compounds. Besides, by first-principles thermodynamics, we have shown that Co tends to occupy the Ni sites as the most favorable configuration, with an increase in the cell parameter and total magnetization as Co content increases, in excellent agreement with experimental measurements. Our findings demonstrate that Co-Ni-based ferrites are soft magnetic materials, which are suitable candidates to be employed in devices that require rapid magnetization and demagnetization