X-ray single crystal study of cobalt-tin containing hexagonal ferrites: BaFe12−2xCoxSnxO19 (x∼1.28) and BaFe4−2ySn2+yCoyO11 (y∼1.32)

Cobalt and tin substituted barium ferrites: the K and R phases

“…In the pseudoternary system (0.4Na 2 O-0.6B 2 O 3 ͒ -BaO-͓(6Ϫx)Fe 2 O 3 ϩxCoSnO 3 ͔ and when enough Fe 2 O 3 has been substituted by CoSnO 3 (Fe 2 O 3 /CoSnO 3 molar ratio equal to 9/3 or even 10/2͒, the region of primary crystallization of Co and Sn substituted barium M-hexaferrite ͓hexagonal system with space group P6 3 /mmc, a ϭ5.9341(2) Å, cϭ23.484(3) Å, Zϭ2] 5 becomes narrow and, with a decrease in the concentration of (0.4Na 2 O-0.6B 2 O 3 ), two different crystalline phases appear; 6 these are the so-called K phase ͓trigonal system with space group P3, aϭ5.9316(7) Å, cϭ14.3128(32) Å, Z ϭ1] 7 and R phase ͓hexagonal system with space group P6 3 /mmc,aϭ6.0294(9) Å, cϭ14.019(5) Å, Zϭ2]. 5 As it is difficult to obtain single crystals of the K and R phases, the characterization of both phases is, at the present time, rare and incomplete. For instance, the R phase has only been studied with polycrystalline samples 4 while the K phase has been studied with single crystal samples but only when H is perpendicular to the crystallographic c axis.…”