Dysprosium (Dy3+)-substituted Ni–Co nanoparticles were synthesized by sol–gel technique. Structural and morphological analyses were accomplished by X-ray diffraction (XRD), scanning electron microscopy (SEM) and field emission transmission electron microscopy (FE-TEM). The crystallite size and lattice parameter followed a decreasing trend up on increase in Dy3+ substitution for the concentration x ≤ 0.15, which is due to the hindrance in crystallite growth and deposition of Dy3+ on grain boundaries, respectively. The lattice strain was increased from 5.027 to 8.814 × \({10}^{-3}\) with enhancement in Dy3+ content. The morphological studies showed uniform distribution of particles with slight agglomeration and the average particle size was calculated to be 22.17 nm, which is in good agreement with XRD results. The magnetic studies were executed by vibrating sample magnetometer (VSM) over a wide range of applied magnetic field. The soft ferrimagnetic nature of these ferrites was revealed by narrow (M–H) curve. The magnetic parameters exhibited decreasing behavior upon increasing amount of substitution. The coercivity (Hc) was recorded to be 1097 Oe for x = 0.00 and saturation magnetization (Ms) was calculated in the range 27.04–40.86 emu/g. The anisotropy constant and magneton number were found to be in the range of 9887–46,703 erg/cm3 and 1.21–1.71 µB, respectively. These properties of prepared ferrites point towards their applicability in magnetic recording instruments, memory, and high-density data storage devices.
