Properties of hard magnetic composite materials
Waldemar Kaszuwara, Artur Witkowski, Marcin Leonowicz Politechnika Warszawska, Wydział Inżynierii Materiałowej, ul. Wołoska 141, 02-507 Warszawa
Annals 4 No. 12, 2004 pages 378-383
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abstract Much effort has been devoted to study of hard magnetic nanocomposites in the last fifteen years. Such materials consist of mixture of nanostructured hard and soft magnetic (usually iron phases). Formation of soft magnetic inclusions leads to remanence enhancement, which usually results in increase of the maximum energy product (BH)max, which is the major property determining the functional properties of hard magnetic materials. In the rare earth - transition metal (RE-M) magnets, appropriate combination of chemical composition can produce material containing Fe precipitates. Unique structure of nanocomposite magnets enables achieving high values of the energy product (BH)max in isotropic, nanocrystalline materials such as Nd-Fe-B, Pr-Fe-B and Sm-Fe-N. Also the material composition the magnetic properties of the nanocomposites substantially depend on the microstructure, which is produced in the course of technological process. Our study proved that application of rapid solidification for the processing of Nd-Fe-B and Pr-Fe-B magnets produces better properties than that of mechanical alloying (Figs. 1-6), because the former enables reduction of oxygen content and better control of crystallite size of both hard and soft magnetic phases. In the case of barium ferrites, processed by mechanical alloying, addition of iron also leads to enhancement of the energy product (Fig. 10). Increase of the (BH)max by 13% was achieved by addition of 5% Fe. Key words: hard magnetic nanocomposites, Nd-Fe-B, Pr-Fe-B, Sm-Fe-N, barium ferrite