A FORC investigation into the effect of Cu additive on magnetic characteristics of Co-Ni alloy nanoparticles

CoNi binary alloy nanoparticles were prepared by using a polyol method. The effect of the Cu additive (acting as the third element) on structural and magnetic properties of the CoNi_50−xCu_x (10 ≤ x ≤ 40) alloy was then studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), magnetometry and first-order reversal curve (FORC) analyses. It was found that a combination of Co-Ni alloy and Cu phases is formed when increasing the Cu content by x = 10 and 20. However, for x = 30 and 40, the resulting compound is obtained in the form of a single-phase ternary alloy. Increasing the Cu content increases the separation between soft and hard phases in the FORC diagram, leading to two distinct magnetic phases in CoNi₁₀Cu₄₀. The FORC data showed that the magnetic interaction between particles was reduced when increasing the Cu content. The reversible and irreversible …