Magnetic and microwave properties of Co_0.5Ni_0.5Fe_2-xSc_xO₄ (0.0 ≤ x ≤ 0.1) nanosized spinel ferrites

The Co_0.5Ni_0.5Sc_xFe_2-xO₄ (x ≤ 0.1), CoNiSc, nanosized spinel ferrites (NSFs) were manufactured by sol–gel approach. The XRD (X-Ray Diffraction), SEM (Scanning Electron Microscope), TEM (Transmission Electron Microscope) and HR-TEM (High-Resolution Transmission Electron Microscope) were implemented to investigate the structural and phase formation. The structure, morphological, and magnetic features of CoNiSc NSFs was investigated. XRD analysis demonstrated the formation of single-phase cubic spinel structure for all samples. The cell parameter is increasing with the increase of Sc³⁺ content. SEM, EDX (Energy dispersive X-ray), TEM, HR-TEM, and XPS (X-ray photoelectron spectroscopy) confirmed the cubic morphology, chemical composition and energy state. The crystallite size has increased from ∼ 24 nm to ∼ 43 nm. Magnetic properties of the products were also explored via analyses of M−H loops registered at 300 and 10 K. The analyses of M−H loops indicate that the present samples display ferrimagnetic behavior at both temperatures. The introduction of Sc³⁺ ions greatly influence the magnetization of Co-Ni ferrite system, which is most explained based on the changes in cations distribution. In comparison to pristine (x = 0.00) sample, it was found that the values of M_s, M_r and magneton Bohr number (n_B) firstly increase for × = 0.02 composition and then reduce with further rising Sc³⁺ ions content (x ≥ 0.04). Main electromagnetic parameters were analyzed in the frequency range from 32 till 50 GHz from obtained reflected/transmitted parameters (S11-S21). It was observed correlation of the Sc concentration and microwave properties. Sc substitution leads to the increase of the resonant frequency (f) from 44 (for sample with x = 0.02) till 47.5 GHz (for sample with x = 0.08) and increase of the resonant amplitude from −18.2 dB (x = 0.02) till –23.1 dB (x = 0.1). The nature of the electromagnetic absorption in CoNiSc has resonant behavior and can be associated with the spin and polarization resonances.