Abstract
BaFe12-xGaxO19 (x ≤ 1.2) hexaferrites were synthesized via the usual ceramic technology. It has been established that with an increase in x, the unit cell and magnetic parameters monotonically decrease. The frequency of natural ferromagnetic resonance firstly decreases from 49.6 GHz down to 49.1 GHz when x = 0.6, and then it increases up to 50.5 GHz. The line width monotonically increases from 3.5 GHz up to 5 GHz. The peak amplitude of the resonant curve changes slightly with the exception of when x = 0.9, when it reaches -16 dB. The 1.3 GHz kOe-1 frequency shift in the bias field is more intensive for small values, when x = 0.3. The decreasing values of the magnetic parameters are a result of the dilution of Fe3+-O2--Fe3+ superexchange interactions. The behavior of the amplitude-frequency characteristics is largely determined through the reduction of uniaxial exchange anisotropy. The prospects of Ga-substituted hexaferrites acting as a material that effectively absorbs the high-frequency electromagnetic radiation are shown.
Highlights
M-type hexagonal ferrites continue to attract the attention of researchers.[1]
The X-ray diffraction data correspond to single-phase samples with a hexagonal unit cell crystal structure and P63/ mmc space group, agreeing well with previous results obtained earlier for solid solutions with substitution by Al3+ and In3+ cations.[37,38,39]
The insignificant decreases in the unit cell parameters and, as a result, the unit cell volumes are caused by insignificant divergences of the values of the ionic radii of Ga3+ (0.62 Å) and Fe3+ (0.64 Å) cations.[40]
Summary
Interest in the M-type BaFe12O19 barium ferrite with a hexagonal structure and its solid solutions substituted with different diamagnetic cations (Al3+, In3+, Ga3+, Sc3+, etc.)[4,5,6] is explained by their good functional properties.[7]. M-type barium hexaferrites have prospective use for the absorption of electromagnetic radiation (EMR) in the microwave range, considering their magnetic properties and the possibilities of their modification through various substitutions, including with nanoparticles. An analysis of M-type barium hexaferrite properties in the microwave range shows that the working range – the range of effective EMR absorption – lies in the centimeter spectral range.[25] The application of substituted M-type barium hexaferrites with a large constant of magnetocrystalline anisotropy as fillers in composite materials allows for the frequency selective absorption of EMR, using the controlled resonances of domain boundaries and the rotation of magnetization (natural ferromagnetic resonance, NFR). The results of this work can find application in ensuring intrasystem and intersystem electromagnetic compatibility and in ensuring the operational reliability of devices and equipment under conditions of increased levels of microwave influence, due to the selective absorption of EMR over the set range of frequencies
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