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Title: Search for new permanent magnetic phases by the reaction crucible analysis and developments of new high through put methods
Author: Gross, Florian
Awarding Body: University of Birmingham
Current Institution: University of Birmingham
Date of Award: 2004
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The present work introduces the development and improvement of high through put methods in the search for new intermetallic phases in multi-component systems as hard magnets. Two techniques, the reaction crucible analysis (RCA) and the reaction sintering analysis (RSA), have been employed and these are based on particular tie lines in a phase diagram and the diffusion paths in the specimens. For the RCA, diffusion couples are used, whereby a solid phase (iron crucible) is in contact with a liquid phase (rare earth - additive melt). During the heat treatment, the intermetallic phases form on the inside surface of the crucible in accordance to the tie lines of the respective phase diagram. The RSA samples are formed by blending, pressing and sintering the powders of pure iron, rare earth and additive. During the heat treatment solid and liquid phases react with each other and the intermetallic phases form as layers around the primary particles. The phases formed have been identified metallographically by the use of the Kerr effect and by EDX-analyses. A further element of this work was the measurement of domain structures, such as Kerr-effect contrast and size, and the correlation with the physical magnetic properties, such as saturation magnetisation and crystal anisotropy. As a result of this work the high through put methods, RCA and RSA, have been proved to be efficient tools for the search for new permanent magnetic phases. 120 unknown multi element systems have been investigated and potentially interesting hard magnetic phases have been found, like the (Fe,Co)I7Sm2, (Fe,In)I7Sm2, (Fe,Sb)I7Sm2, (Fe,Sn)I7Sm2 phases with visible domain structures or the binary Fe3Sc phase with a strong in contrast uniaxial domain pattern. Also very promising were the Fe13Pr6Ag and Fe13P~6CU phases with strong in contrast broken like domain patterns and the Fe 13Pr6Si , FeJ3PrJn and FeJ3Pr6Mo phases with strong in contrast unidirectional domain structures. Apart the direct correlation between the contrast of uniaxial domain structures and the saturation magnetisation of the corresponding phases, a possible correlation between the domain size and the crystal anisotropy has also been shown.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available