La-Zn Substituted Hexaferrites Prepared by Chemical Method
La-Zn substituted M-type Ba hexaferrite powders were prepared by sol-gel (Mx) and organometallic precursor (Sk) methods with Fe/Ba ratio of 11.6 and 10.8, respectively. The compositions (LaZn)xBa1−x Fe12−x O19 with 0.0 ≤ x ≤ 0.6 were annealed at 975°C/2 h. The cationic site preferences of nonmagnetic La3+ instead of Ba2+ ions and Zn2+ instead of Fe3+ ions were determined by Mössbauer spectroscopy. The La3+ ions substitute the large Ba2+ ions at 2a site and for x ≥ 0.4 also at 4f2 site. The nearly all Zn2+ ions are placed at the 4f1 sites. The thermomagnetic analysis of χ(ϑ) confirms that only the small substitutions for x ≤ 0.4 can be taken as a single-phase hexaferrites. The coercivity H c almost does not change at x = 0.2 for (Mx) samples and further decrease up to x = 0.6. For (Sk) samples at substitution x = 0.2 the values of H c are decreasing and at higher x the values nearly do not change. The Curie points, T c, slowly decrease with x for both (Mx) and (Sk) samples.
Key wordsferrites-hexagonal magnetic recording Mössbauer effect
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