Formation of submicron-sized SrFe12−xAlxO19 with very high coercivity

Synthesis and Characterization of PEG-Sr Hexaferrite by Sol–Gel Conversion

“…It is a hard magnet with high coercivity, which originates from high magnetocrystalline anisotropy with single easy magnetization axis. It has been recognized that it can be used as permanent magnets, recording media, telecommunication, and as components in microwave, higher-frequency, and magnetooptical devices [35][36][37][38][39][40][41].…”

Structure and Magnetic Properties of Submicrocrystalline Powders of Strontium Hexaferrite and Magnets Based on Them

“…Variation of the initial composition of the glasses and of the modes of their heat treatment makes it possible to control the size and shape of the particles of SrFe 12 O 19 precipitating during crystallization. Values of Hci approaching the theoretical limit (H ci = 10.18 kOe for particles of SrFe 10.7 Al x -1.3 O 19 ) have been obtained for glass ceramic specimens [5]. The synthesized material is a composite where hard magnetic particles of SrFe 12 O 19 are distributed in a nonmagnetic SrB 2 O 4 matrix.…”

“…The x-ray diffraction analysis performed shows that the amorphous phase has decomposed fully, and the structure of the annealed specimen contains 31 vol.% SrFe 12 O 19 and 69 vol.% SrB 2 O 4 . Comparison of the parameters of the crystal lattice of phase SrFe 12 O 19 (a = 0.584 nm, c = 2.293 nm) with the data of [5,9] allows us to assume that the interaction between the melt and the walls of the alundum crucible during the melting causes alloying of the glass with aluminum. According to the data of the microscopic x-ray diffraction analysis the content of aluminum in the obtained glass ceramics is about 4 wt.%.…”

Preparation of magnetic composites through SrO-Fe2O3-Al2O3-B2O3 glass crystallization

“…The H c of samples 1 is a nonmonotonic function of annealing temperature, with a maximum (650 kA/m) at t ann = 850°C. The rise in coercivity below this temperature is attributable to the increase in the size and thickness-to-diameter ratio of single-domain hexaferrite particles and the rise in the degree of aluminum substitution for iron in the hexaferrite [3,8]. The most likely reason for the drop in the coercivity of samples 1 is that high-temperature annealing of these samples leads to the formation of large, multidomain hexaferrite particles [9], as will be shown below.…”

“…In a recent report [3], we described the preparation of magnetic glass-ceramics based on aluminum-doped strontium hexaferrite through 13SrO · 5. ) (all of reagent grade).…”