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Metals 2014, 4(1), 8-19; doi:10.3390/met4010008
Article

Magnetism-Structure Correlations during the ε→τ Transformation in Rapidly-Solidified MnAl Nanostructured Alloys

1
, 1
, 1
, 2
, 2
 and 1,*
1 Department of Chemical Engineering, Northeastern University, 360 Huntington Ave., Boston, MA 02115, USA 2 Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7204, USA
* Author to whom correspondence should be addressed.
Received: 13 December 2013 / Revised: 14 January 2014 / Accepted: 16 January 2014 / Published: 21 January 2014
(This article belongs to the Special Issue Manganese-based Permanent Magnets)
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Abstract

Magnetic and structural aspects of the annealing-induced transformation of rapidly-solidified Mn55Al45 ribbons from the as-quenched metastable antiferromagnetic (AF) ε-phase to the target ferromagnetic (FM) L10 τ-phase are investigated. The as-solidified material exhibits a majority hexagonal ε-MnAl phase revealing a large exchange bias shift below a magnetic blocking temperature TB~95 K (Hex~13 kOe at 10 K), ascribed to the presence of compositional fluctuations in this antiferromagnetic phase. Heat treatment at a relatively low annealing temperature Tanneal ≈ 568 K (295 °C) promotes the nucleation of the metastable L10 τ-MnAl phase at the expense of the parent ε-phase, donating an increasingly hard ferromagnetic character. The onset of the ε→τ transformation occurs at a temperature that is ~100 K lower than that reported in the literature, highlighting the benefits of applying rapid solidification for synthesis of the rapidly-solidified parent alloy.
Keywords: nanostructured magnetic materials; Mn-based magnets; rapid-solidification nanostructured magnetic materials; Mn-based magnets; rapid-solidification
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Jiménez-Villacorta, F.; Marion, J.L.; Oldham, J.T.; Daniil, M.; Willard, M.A.; Lewis, L.H. Magnetism-Structure Correlations during the ε→τ Transformation in Rapidly-Solidified MnAl Nanostructured Alloys. Metals 2014, 4, 8-19.

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