Impact of Tm ³⁺ and Tb ³⁺ Rare Earth Cations Substitution on the Structure and Magnetic Parameters of Co-Ni Nanospinel Ferrite

Abstract

Tm-Tb co-substituted Co-Ni nanospinel ferrites (NSFs) as (Co _0.5Ni _0.5) [Tm _xTb _xFe _2−2x]O ₄ (x = 0.00–0.05) NSFs were attained via the ultrasound irradiation technique. The phase identification and morphologies of the NSFs were explored using X-rays diffraction (XRD), selected area electron diffraction (SAED), and transmission and scanning electronic microscopes (TEM and SEM). The magnetization measurements against the applied magnetic field (M-H) were made at 300 and 10 K with a vibrating sample magnetometer (VSM). The various prepared nanoparticles revealed a ferrimagnetic character at both 300 and 10 K. The saturation magnetization (M _s), the remanence (M _r), and magneton number ( $n_B$ ) were found to decrease upon the Tb-Tm substitution effect. On the other hand, the coercivity (H _c) was found to diminish with increasing x up to 0.03 and then begins to increase with further rising Tb-Tm content. The H _c values are in the range of 346.7–441.7 Oe at 300 K to 4044.4–5378.7 Oe at 10 K. The variations in magnetic parameters were described based on redistribution of cations, crystallites and/or grains size, canting effects, surface spins effects, super-exchange interaction strength, etc. The observed magnetic results indicated that the synthesized (Co _0.5Ni _0.5)[Tm _xTb _xFe _2−x]O ₄ NSFs could be considered as promising candidates to be used for room temperature magnetic applications and magnetic recording media.