Dielectric, XPS, and ferromagnetic relaxation studies of Ho-substituted polycrystalline magnetic oxide materials

• Published in: Ceramics international 2022-11, Vol.48 (21), p.32266-32272
• Main Authors: Manzoor, Alina, Azhar Khan, Muhammad, Afzal, Amir Muhammad, Arshad, Muhammad Imran, Shahzad, Aamir, Akbar, Sofia, Kashif, Muhammad, Ashraf, Ghulam Abbas, Khan, Muhammad Yaqoob, Rasul, M. Nasir, Shifa, Muhammad Shahzad, Nasar, Gulfam, Hussain, Altaf
• Format: Article
• Language: English
• Subjects: FMR linewidth; Nanomaterials; Resistivity; Seebeck coefficient; XPS
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2022.07.168

The impact of holmium (Ho) ions on lithium-rich spinel ferrites is studied through magnetic, morphological, and electrical transport properties. The X-ray photoelectron spectroscopy (XPS) analysis indicated the existence of all metal ions in the required valence state. Transmission electron microscopy (TEM) analysis exhibited nano-crystalline (∼50 nm) structures of these ferrites. The electrical resistivity measurements showed the higher resistivity values of the synthesized samples. The resistivity increased from 2.4 × 108 to 2.1 × 1010 Ω-cm with Ho inclusion, indicated an inverse relation with the size of grains. The Curie temperature (Tc) observed to decrease from 848 to 806 K with the incorporation of Ho3+ions. The activation energy (ΔEa) noted to vary between 0.21 and 0.23 eV. The drift mobility (μd) study revealed a decrease from 1.86x10−12to 6.14x10−14cm2V−1s−1by increasing Ho amount up to x = 0.06. A reduction in thermoelectric power (S) from -143 to -95 μ.V/K by increase in Ho concentration confirmed the Fe replacement by Ho on octahedral B-sites. The ferromagnetic resonance (FMR) investigations indicated a drop in FMR line-broadening (ΔH) from 2491 to 2000 Oe by the increase of Ho concentration, making it beneficial to reduce microwave losses. A non-linear variation in the resonance field (Hres) with the substitution of Ho was observed between 7359 to 7785 Oe.