Impact of Nd3+ Substitutions on the Structure and Magnetic Properties of Nanostructured SrFe12O19 Hexaferrite

In this study, SrFe_12-xNd_xO₁₉, where x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5, was prepared using high-energy ball milling. The prepared samples were characterized by X-ray diffraction (XRD). Using the XRD results, a comparative analysis of crystallite sizes of the prepared powders was carried out by different methods (models) such as the Scherrer, Williamson-Hall (W-H), Halder-Wagner (H-W), and size-strain plot (SSP) method. All the studied methods prove that the average nanocrystallite size of the prepared samples increases by increasing the Nd concentration. The H-W and SSP methods are more accurate than the Scherer or W-H methods, suggesting that these methods are more suitable for analyzing the XRD spectra obtained in this study. The specific saturation magnetization (σ_s), the effective anisotropy constant (K_eff), the field of magnetocrystalline anisotropy (H_a), and the field of shape anisotropy (H_d) for SrFe_12-xNd_xO₁₉ (0 ≤ x ≤ 0.5) powders were calculated. The coercivity (H_c) increases (about 9% at x = 0.4) with an increasing degree of substitution of Fe³⁺ by Nd^3+, which is one of the main parameters for manufacturing permanent magnets.

Novel ferrimagnetic nanomaterial Sr(1−x)LaxGdySmzFe(12−(z+y))O19 for recording media applications: experimental and theoretical investigations

Developed novel ferrimagnetic nanomaterial Sr_(1−x)La_xGd_ySm_zFe_(12−(z+y))O₁₉ has a significant function in industry, which could be beneficial for recording media applications.

New nanosized Gd-Ho-Sm doped M-type strontium hexaferrite for water treatment application: experimental and theoretical investigations

In this paper, rare-earth doped M-type strontium hexaferrite magnetic nanoparticles SrHo_xGd_ySm_zFe_{(12−(x+z+y))}O₁₉ (x = y = z = 0.01) have been prepared by the sol–gel combustion method for the first time. The properties of the material were investigated using XRD, FTIR spectroscopy, Raman spectroscopy, SEM, UV-Vis spectroscopy, and VSM. X-ray analysis revealed that a magnetic single-phase was formed with a crystallite average size of 49 nm. FTIR spectra confirmed the formation of the structure of the hexaferrite phase. Raman analysis confirmed the formation of all crystallographic hexaferrite sites. A shift in the octahedral site frequencies and a significant shift were observed at site 12k and 2a, indicating that the doping elements occupied these sites. The SEM analysis showed that the particles were different in shape and slightly agglomerated. The EDS result confirmed the purity of the sample. The calculated band gap from the UV-Vis NIR spectroscopy spectra of the sample was 1.62 eV. The magnetic analysis of the sample material at room temperature revealed a coercivity of 5257.63 Oe, saturation magnetization of 67.72 emu g⁻¹, remanence ratio of 0.52, a maximum magnetic energy product of 1.06 MGOe and Curie temperature of T_c = 765 K. First-principles calculations were conducted on multiple configurations of SrFe_12−xX_xO₁₉ with x = 0, 0.5 and X = Sm, Gd, Ho. The site preference of each doping element was determined, and the effect of the doping on the structural, electronic, and magnetic properties of the compound was studied. The magnetic properties of this rare earth (Gd, Ho, Sm) doped strontium hexaferrite indicated that this compound could be used in both permanent magnets and water treatment application.

Development of the new nanohexaferrite SrHo_0.01Gd_0.01Sm_0.01Fe_11.97O₁₉ for important applications in industry, which could be very beneficial for applications in magnetic water treatment.

Impacts of Sol-Gel Auto-Combustion and Ultrasonication Approaches on Structural, Magnetic, and Optical Properties of Sm-Tm co-Substituted Sr0.5Ba0.5Fe12O19 Nanohexaferrites: Comparative study

In this paper, we introduced a comparative study of Sm-Tm-substituted Sr-Ba nanohexaferrites (NHFs), Sr0.5Ba0.5TmxSmxFe12-2xO19 with x = 0.00-0.05, manufactured via both citrate sol-gel auto-combustion and ultrasonication approaches. The phase formation of M-type hexaferrite (HF) for both compositions was confirmed by X-ray diffraction (XRD) powder pattern, Fourier-transform infrared (FT-IR) spectra, scanning and transmission electron microscopy (SEM and TEM) micrographs, energy dispersive X-ray (EDX) spectra, and elemental mappings. The magnetic properties at room temperature (RT) and low temperature (T = 10 K) were also investigated. M-H loops revealed ferrimagnetic nature for various prepared nanohexaferrites via sol-gel and ultrasonication routes. The Ms (saturation magnetization) and Mr (remanence) values increased with increasing Tm-Sm substituting contents. Ms and Mr reached their maximum values at x = 0.04 in the case of samples prepared using the sol-gel technique and at x = 0.03 for those prepared via ultrasonication route. M-H loops were very broad in samples prepared via ultrasonication route in comparison to those produced by means of the sol-gel approach, implying that the products synthesized via ultrasonication route have greater values of coercivity (Hc). The variations in Hc values with respect to Tm-Sm substitutions were governed by the evolutions in the magneto-crystalline anisotropy. Diffuse reflectance spectra (DRS) were employed to estimate the direct band gap of pristine and co-substituted Sr0.5Ba0.5Fe12O19 hexaferrites. Optical energy band gaps (Eg) of pristine samples were significantly tuned by co-substitution of Tm3+ and Sm3+ ions. Eg values of the Sr0.5Ba0.5Fe12O19 sample, which was synthesized using the sol-gel method, decreased almost linearly from 1.75 to 1.45 eV by increasing co-doped ion content. However, we observed a sharp drop from 1.85 eV to an average of 1.50 eV for the samples, which were synthesized using the ultrasonication approach.

Structural studies of CaAl12O19, SrAl12O19, La2/3+δ Al12–δO19, and CaAl10NiTiO19 with the hibonite structure; indications of an unusual type of ferroelectricity

Various oxides with the hibonite structure were synthesized and structurally analyzed using powder neutron diffraction. The structure of CaAl12O19 at 298 and 11 K shows dipoles that are apparently too dilute to order unless subjected to a suitable electric field. Magnetoplumbites, such as BaFe12O19, are isostructural with hibonite. These compounds possess ferromagnetic properties, which combined with the electric dipoles may influence multiferroic behavior. Our SrAl12O19 sample showed two distinct hexagonal phases, a major phase with the normal hibonite structure and a minor phase having a closely related structure. Our sample of the defect hibonite phase La2/3+δAl12–δO19 shows a distinctly higher δ value (0.25) vs. that reported (~0.15) for samples made from the melt. Finally, we used to advantage the negative scattering length of Ti to determine the site occupancies of Ni and Ti in CaAl10NiTiO19.

BaGa4O7, a new A3BC10O20 crystalline phase: synthesis, structural determination and luminescence properties

A new compound, BaGa₄O₇, is found by cooling from the melt. Part of the A₃BC₁₀O₂₀ family, it exhibits strong orange-red luminescence emission when doped with Eu³⁺.