Magnetic and Terahertz-Infrared Properties of Nanodispersed Hexaferrite Sr_xBa_(1-x)Fe₁₂O₁₉ Solid Solutions

Hexagonal ferrites with the formula SrxBa(1-x)Fe12O19 (x = 0; 0.3; 0.5; 0.7; and 1) were prepared using the citrate method. The main feature of this synthesis is a relatively low calcination temperature of 700 degrees C. An X-ray diffraction study revealed a single-phase material. According to SEM, the particles were 50-70 nm in diameter. The Curie temperature of the samples that were determined using the DSC method varied in a very narrow range of 455-459 degrees C. Analysis of the magnetic hysteresis loops obtained at 300 K and 50 K indicated all samples as magnetically hard materials in a single-domain state. The maximal magnetic characteristics encompass strontium hexaferrite. The terahertz spectra of complex dielectric permittivity and the spectra of infrared reflectivity were measured at room temperature in the range of 6-7000 cm-1. The obtained broad-band spectra of the real and imaginary parts of permittivity reveal significant changes associated with structural distortions of the (Sr,Ba)O-12 anti-cuboctahedron caused by the substitution of Ba2+ with Sr2+ in the same crystallographic positions.