Impact of Al3+ ions on magnetic and microwave properties of BaM:Ti hexaferrites

Abstract BaFe(11.5-x)Ti0.5AlxO19 (0.1 x 3.0) samples were produced using solid state reaction method. Systematic studies of the crystal structure parameters, magnetic and microwave properties were carried out. All samples were single phase and described by the P63/mmc space group. It was established that an increase in the content of Al3+ ions in BaFe(11.5-x)Ti0.5AlxO19 (or BaM:Ti, where BaM – M-type barium hexaferrite) leads to a decrease in the lattice parameters and density of the samples. This correlates well with the ionic radii and atomic weight of Fe3+ and Al3+ ions. The weakening of Fe3+-O-Fe3+ exchange interactions induced a decrease in the temperature of the magnetic phase transition and saturation magnetization. The microwave properties as well as the frequency dependences of the permittivity and permeability in the range from 0.1 to 18 GHz were discussed in terms of the resonance of domain boundaries. A strong correlation between Al3+ concentration, crystal structure, magnetic and microwave properties was shown for BaFe(11.5-x)Ti0.5AlxO19 (0.1 x 3.0) samples.