Structural and magnetic properties of RE-Al substituted nanocrystalline hexaferrites (Sr_1−xRE_xAl₂Fe₁₀O₁₉)

Abstract

We describe the synthesis and characterization of magnetic materials with improved magnetic properties for permanent magnet applications. Sr 1−x RE x Al 2 Fe 10 O 19 (RE=La, Ce, Tb, and Dy; x=0.0 and 0.1) were prepared by ball milling and sintering at 1200°C for 6 h. The effects of (Al 3+ -RE 3+ ) substitution on the structural and magnetic properties of SrM hexaferrites were investigated by x-ray diffraction, scanning electron microscopy, and magnetic measurements at low (5 K), and high temperatures (from room temperature to above Curie temperature). The sample with x=0, and that with La substitution, consisted of a single SrM phase. The rest of the samples contained traces of secondary oxide phases, and exhibited a small reduction in lattice parameters compared with the unsubstituted SrFe 12 O 19 . The coercivity of the samples (8800H cM 9750 Oe) was more than double the standard value of the unsubstituted compound, and the Curie temperatures was >300°C for all samples. Also, the saturation magnetization (32.5-46.4 emu g −1 ) was high enough to make the overall magnetic properties of these compounds potentially important for the permanent magnet industry.

Recent Progress in Hexagonal Ferrites Based Composites for Microwave Absorption

“…[60] They were discovered and characterized in the early 1950s, and their practical value has sparked an exponential increase in attention since then. [61][62][63][64][65][66][67][68][69] They are among the most researched materials in high-frequency devices. [69][70][71][72] They are ideal for applications such as radar absorption materials due to their high permeability, [73] high saturation magnetization, high coercivity, [74,75] strong chemical stability, good resistivity, and low eddy current losses.…”

Effects of pH value and Sintering Temperature on the Structural and Magnetic Properties of Barium Hexaferrites Prepared by Co-Precipitation

“…Alternatively, researchers have used special substitution scenarios to produce M-type hexaferrites with high coercivities suitable for high quality permanent magnets. [15][16][17][18][19][20][21] However, in several cases, the improvement of the coercivity was accompanied by some drawbacks such as unfavorable decrease of the saturation and remnant magnetizations, the use of expensive rare-earth elements, and elaborate experimental procedures. [20][21][22][23][24] Co-precipitation technique was reported to be successful for the preparation of M-type hexaferrites with controlled particle size distribution and enhanced coercivity at low sintering temperatures.…”

“…[15][16][17][18][19][20][21] However, in several cases, the improvement of the coercivity was accompanied by some drawbacks such as unfavorable decrease of the saturation and remnant magnetizations, the use of expensive rare-earth elements, and elaborate experimental procedures. [20][21][22][23][24] Co-precipitation technique was reported to be successful for the preparation of M-type hexaferrites with controlled particle size distribution and enhanced coercivity at low sintering temperatures. [25][26][27] The effects of stoichiometry, heat treatment, and pH on the formation of the hexaferrite phase and its magnetic properties were addressed by several researchers.…”