Abstract
MnAl-C is a prominent candidate for the replacement of rare earth magnets with a moderate energy density product. Crystallographic defects have a strong effect on magnetization properties. In this work, we show the influence of twinning defects in the nanometer regime on the quality of the magnet. Standard micromagnetic simulations and computations of the saddle point configuration for magnetization reversal highlight the importance of optimizing the fraction of and reducing the width of crystallographic twin defects. Switching field distributions and the maximum possible coercive field for ideal microstructures without defects are estimated using a reduced order micromagnetic model.
Highlights
The removal or reduction of critical rare earth elements in permanent magnets is of utmost importance to ensure economically and ecologically sustainable applications
MnAl-C is a prominent candidate for the replacement of rare earth magnets with a moderate energy density product
We tune the density of twin boundaries for a high energy density product
Summary
The removal or reduction of critical rare earth elements in permanent magnets is of utmost importance to ensure economically and ecologically sustainable applications. MnAl-C has promising magnetic characteristics filling the gap between strong rare earth based magnets and weak ferromagnets, yet currently achieved coercivities are rather low.. Several intergranular defects induce pinning and nucleation sites.. The various processes to fabricate MnAl-C compounds influence the amount and density of such crystallographic defects and the magnetic characteristics of the material. During hot-extrusion of MnAl-C, a drastic reduction of the grain size can be observed due to a dynamic recrystallization process.. Remaining larger grains contain a large amount of lamellar twin structures with a few nm in width (Fig. 2). The material composition at those twin boundaries is inhomogeneous as recently published in Ref. 8
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