Creation and Magnetic Study of Ferrites with Magnetoplumbite Structure Multisubstituted by Al3+, Cr3+, Ga3+, and In3+ Cations

Abstract

Multisubstituted barium ferrites with a magnetoplumbite structure were obtained by the method of solid-phase reactions with ferritization and pre-firing. Three-charged, mainly diamagnetic cations Al3+, Cr3+, Ga3+, and In3+ were chosen as substituents for the Fe3+ iron cations, the proportion of which in solid solutions did not exceed 50%. The values of the configurational mixing entropy were calculated for all the compositions. A slight deviation of the chemical composition of the obtained solid solutions from the nominal value was established by the energy-dispersive X-ray spectroscopy method. The phase purity and values of the unit cell parameters were refined from X-ray scattering data using full-profile analysis in the Rietveld method. A non-monotonic behavior of the unit cell parameters as a function of the B-sub-lattice average ionic radius of the magnetoplumbite structure was found. A minimum unit cell volume of ~667.15 Å3 was found for the composition BaFe6.11Al1.56Cr2.17Ga2.16O19 with a B-sub-lattice average ionic radius of ~7.449 Å. The average crystallite size varied within 5.5–6.5 μm. The temperature and field dependencies of the magnetization have been measured. The values of the saturation magnetization, residual magnetization, hysteresis loop squareness, and coercivity at 50 K and 300 K were extracted from the experimental data. Using the Law of Approach to Saturation, the magnetic crystallographic anisotropy coefficient and anisotropy field were calculated. Multisubstitution leads to a significant decrease in such magnetic parameters as the magnetic ordering temperature and spontaneous magnetization at both temperatures. The maximum magnetic ordering temperature of ~297.7 K was found for the composition BaFe5.84Ga6.19O19 with a B-sub-lattice average ionic radius of ~7.586 Å in a field of 500 Oe. A maximum saturation magnetization of ~24.7 emu/g was found for the composition BaFe5.84Ga6.19O19 with a B-sub-lattice average ionic radius of ~7.586 Å at 50 K. A maximum hysteresis loop squareness of ~0.72 was found for the composition BaFe6.11Al1.56Cr2.17Ga2.16O19 with an average ionic radius of ~7.449 Å at 50 K. A maximum magnetic crystallographic anisotropy coefficient of ~2.09 × 105 Erg/g was found for the composition BaFe6.19Al1.25Cr1.57Ga1.74In1.26O19 with a B-sub-lattice average ionic radius of ~7.706 Å at 50 K. The frustrated magnetic state including the nano-sized clusters with an average diameter in the range of 50–200 nm was established from the results of measuring the ZFC and FC temperature magnetizations. The interpretation of the obtained experimental data is carried out taking into account the increased stability of high-entropy phases and regular changes in the intensity of the Fe3+(Al3+, Cr3+, Ga3+, In3+)–O2−–Fe3+(Al3+, Cr3+, Ga3+, In3+) indirect superexchange interactions as a result of magnetic dilution of the iron sub-lattice in the magnetoplumbite structure.

Fabrication of doped ferrites and exploration of their structure and magnetic behavior

“…Such a form of hysteresis loops is observed for materials consisting of nanosized crystallites. 92 It can be concluded that the energies of magnetic anisotropy and thermal fluctuations are comparable for the studied samples. 93 With an increase in the concentration of manganese ions, the coercivity and remanence decrease, and become almost equal to zero for x = 0.6.…”

Cr2O3 Promoted In2O3 Catalysts for CO2 Hydrogenation to Methanol

“…Meanwhile, the diffraction peaks of In 2 O 3 were shifted to high angles (Figure 2b). It has reported that the radius of In 3+ (0.800 Å) is larger than that of Cr 3+ (0.615 Å) [20] . When Cr is incorporated into the In 2 O 3 lattice, significant shrinkage of the unit cell and thus a high angle shift of the diffraction peaks can be observed.…”

“…It has reported that the radius of In 3 + (0.800 Å) is larger than that of Cr 3 + (0.615 Å). [20] When Cr is incorporated into the In 2 O 3 lattice, significant shrinkage of the unit cell and thus a high angle shift of the diffraction peaks can be observed. Therefore, the absence of Cr 2 O 3 diffraction peaks might indicate that the In 2-x Cr x O 3 solid solutions were formed in these samples.…”

Phase transition enhanced electromagnetic wave absorption in Cs(Pb,Fe,Co,Ni,Mn)Br3‐based high‐entropy compounds

“…Figure 8A indicates an increase in coercivity with M content. Magnetic coercivity is primarily influenced by crystal structure and anisotropy, leading to preferred magnetization directions that challenge altering magnetic alignment 8–12 . Conversely, crystal defects and grain boundaries act as pinning sites, making it more difficult for magnetic domains to reorient and thus increasing coercivity 12–16 …”

“…For example, the rare-earth ions doped A-site (Sm, Eu, Gd, Er) in CrMnFeCoNiO 3 or CoFe 2 O 4 ferrites, [4][5][6] the doping at B site i.e. Se doped NiFe 2 O 4 , 7 Co-Ni doped Co 0.5 Ni 0.5 Fe 2−x Ga x O 4 , 8 or multi-cations or polysubstituted high entropy both in A and B sites of complex ferrites, such as Fe/Ti/Al/Mn/Co/In/Ga/Cr, 9 Al/Cr/Ga/In, 10 Ti/In/Ga/Cr/Co/Fe, 11 La/Nd/Cr/Mn/Fe/Co/Ni, 12 and Mg/Ga-Mg/Fe. 13 The exploration of transition metal ions' impact on the EMA of complex ferrites has shown promise in the highfrequency range.…”