Effect of calcination temperature and cobalt addition on structural, optical and magnetic properties of barium hexaferri
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Effect of calcination temperature and cobalt addition on structural, optical and magnetic properties of barium hexaferrite BaFe12O19 nanoparticles Khulud Habanjar1 · Haneen Shehabi1 · A. M. Abdallah1 · R. Awad1 Received: 8 January 2020 / Accepted: 24 March 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract (xCo)-BaFe12O19 nanoparticles, with 0 ≤ x ≤ 0.1 wt%, have been prepared using a chemical co-precipitation method and different calcination temperatures (850 °C, 900 °C and 950 °C). The samples were subjected to structural, optical and magnetic studies. X-ray powder diffraction showed the hexagonal crystal structure of (xCo)-BaFe12O19, and the more convenient temperature for the formation of this phase was 950 °C. Transmission electron microscope was used for investigating the morphology as well as the average particle size of the samples. It was found that the average size of all samples ranges between 65 and 90 nm. The energy band gap Eg was determined using UV–Vis spectroscopy. It was noticed that the values of Eg decreased with the addition of cobalt and the increase in the calcination temperature. The M–H curve obtained from vibrating sample magnetometer has been used to study the magnetic behavior. The anisotropy field (Ha), the saturation magnetization (σs), the effective crystalline anisotropy constant (Keff), the remanent magnetization (σr) and squareness ratio (S) for each sample were calculated. The maximum value of coercivity (5087Oe) was found for x = 0 wt% at T = 950 °C which is suitable for magnetic applications, such as the recording equipment and permanent magnets. Keywords Barium hexaferrites · Co-precipitation · Energy gap · M–H loop · Coercivity
1 Introduction Regarded as hard magnetic materials, M-type barium hexaferrites (BaM) have attracted much attention for numerous applications. They possess high saturation magnetization and coercivity, a large uniaxial anisotropy and an exceptional magnetic permanence. Barium hexaferrites are widely used in high-density magnetic recording media, magnetic microwaves and sound waves devices, supercapacitors as well as magnetic hose, mainly formed of a paramagnetic shell with a ferromagnetic core, in the guidance and transport of magnetic fields to large distances [1–5]. BaFe12O19 has a magnetoplumbite structure. Its unit cell consists of dual structure blocks (RSR*S*), with a lattice formed of oxygen and iron ions, aligned in the direction of the hexagonal c-axis (* indicates the block’s rotation by 180° * Khulud Habanjar [email protected] 1
Department of Physics, Faculty of Science, Beirut Arab University, P.O. Box 11‑5020, Riad El Solh, Beirut, Lebanon
with respect to c-axis). In R block, oxygen ions are packed in a closed hexagonal structure and iron ions occupy the octahedral, tetrahedral and the bipyramidal sites. However, in S block oxygen ions are packed in a cubic lattice and iron ions are distributed on the tetrahedral and octahedral sites [6]. It is well known that the distributions of Fe ions between the inte
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