A study on the order–disorder phase transformations of rapidly solidified Sm–Co-based permanent magnets |
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Authors: | S. Aich J.E. Shield |
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Affiliation: | Department of Mechanical Engineering and Center for Materials Research and Analysis, University of Nebraska, Lincoln, NE 68588-0656, USA |
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Abstract: | The structural transformation from the metastable, disordered TbCu7-type SmCo7 structure to the equilibrium, ordered Th2Zn17-type Sm2Co17 structure was revealed by X-ray diffraction analysis using Rietveld refinement. The magnetic properties depended strongly on the stage of the transformation, as the coercivity depended on the annealing temperature. The as-solidified alloys in the TbCu7-type structure exhibited coercivity as high as 7.85 kOe, which increased to greater than 9 kOe after heat treatment. The magnetization processes were also strongly influenced by the structural state. Initially it was dominated by nucleation processes, which gave way to domain wall pinning-controlled magnetization processes with the development of the Sm2Co17 structure. Transmission electron microscopy revealed the development of antiphase domains during heat treatment, which apparently served as the domain-wall pinning sites during magnetization reversal. |
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Keywords: | 75.01.A 89.02 07.55 85.70 |
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