Influence of annealing temperature and Co substitution at B-site for Fe³⁺ ions on the physicochemical characteristics of HoFeO₃ perovskite nanoparticles

This work studies the influence of annealing temperature and Co-doping at the Fe-site on the physicochemical characteristics of nanosized perovskite HoFe_1−xCo_xO₃ (with theoretical doping levels of x = 0.05, 0.15, and 0.25), synthesized via a simple co-precipitation technique. The substitution of Co at the Fe-site reduces both the average crystallite size and lattice volume. This reduction is attributed to the smaller ionic radius of ₂₇Co³⁺ (0.55 Å in low-spin, 0.61 Å in high-spin) compared to that of ₂₆Fe³⁺ (0.65 Å in high-spin). Co-doping significantly enhances the magnetic properties of HoFe_1−xCo_xO₃ by increasing the crystalline anisotropy, leading to improved coercivity (H_c) and remanent magnetization (M_r). Incontrast, higher annealing temperatures improve crystallinity, leading to decreased H_c and M_r. The synthesized HoFe_1−xCo_xO₃ nanoparticles exhibit characteristics of hard magnetic materials, displaying higher H_c and M_r compared to similar reported perovskites such as Ni-doped HoFeO₃, Co-doped NdFeO₃, Ni/Mn-doped YFeO₃, and Ni-doped LaFeO₃. These findings suggest that these HoFe_1−xCo_xO₃ nanomaterials possess promising potential for the fabrication of permanent magnets, particularly in magnetic recording applications, such as in hard drives and magnetic tapes.