Special Issue "Manganese-based Permanent Magnets"
A special issue of Metals (ISSN 2075-4701).
Deadline for manuscript submissions: closed (31 March 2015)
There is a significant gap between the energy product, BHmax, of both the traditional ferrite and AlNiCo permanent magnets of less than 10 MGOe and that of the rare earth magnets of greater than 30 MGOe. This is a gap that Mn-based magnets could potentially fill inexpensively. This special issue presents work on the development of both MnAl and MnBi permanent magnets. Some of the challenges involved in the development of these magnets include improving the compounds’ energy product, increasing the thermal stability of these metastable compounds, and producing them in quantity as a bulk material. These challenges are addressed from both experimental and theoretical points of view in the papers presented here.
Prof. Dr. Ian Baker
Manuscript Submission Information
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- permanent magnets
- Mn-based magnets
- maximum energy product
The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.
Type of Paper: Article
Title: Options for Manganese-Based Alloys as Permanent Magnets
Author: Steve Constantinides
Affiliation: Arnold Magnetic Technologies Corp. 770 Linden Avenue, Rochester, NY 14625, USA
Abstract: Binary and ternary alloys of the naturally ferromagnetic elements (iron, nickel and cobalt) have been exhaustively investigated for use as permanent magnets. A limited number of binary manganese alloys has also been investigated most notably MnAl and MnBi. An attempt to commercialize MnAl was made in 1979 by Matsushita. Shortly after the announcement of their product, neodymium iron boron was discovered and work on the manganese alloys ceased. With shortages and high prices of the rare earth elements, there is a renewed interest in Mn-based alloys. This work will review past investigation into Mn alloys for magnets and identify the potential for commercialization of the more promising alloys.
Title: Effect of Compositions and Heat Treatment on Magnetic Properties of MnBi
Author: Jun Cui
Affiliation: Pacific Northwest National Laboratory, PO Box 999, Richland, WA 99352, USA
Abstract: MnBi has the potential to replace some of the rare-earth based permanent magnetic material. The coercivity of MnBi increases with increasing temperature, making it a good candidate for high temperature application. MnBi itself has relatively low saturation magnetization, about 8 kG at room temperature and 7 kG at 200°C. It must be exchange coupled with soft phases such as FeCo or Co to attain higher magnetization and higher energy product. The first step toward MnBi based composite magnet is to obtain high quality hard phase in large quantity and in submicron sizes. However, MnBi is difficult to obtain in high purity, partly because the reaction between Mn and Bi is peritectic, and partly because Mn reacts readily with oxygen. In addition there is a eutectic reaction at 262°C, which causes MnBi to decompose during the bulk magnet fabrication process. Compositions and heat treatments have drastic effect to the phase contents and magnetic properties of the obtained MnBi material. In this paper, we report our effort on obtaining high performance MnBi hard phase through composition and heat treatment optimization. To date, high purity MnBi (>90%) can be routinely produced in large quantity. The optimum composition is Mn55.9Bi44.1. The heat treated powder exhibits 74 emu/g saturation magnetization at room temperature with 9 T applied field. After proper alignment, the energy product of the powder reached 11.9 MGOe, and that of the sintered bulk magnet reached 7.8 MGOe at room temperature.