Nanocrystalline Sm-based 1:12 magnets

Schönhöbel, A.M. and Madugundo, R. and Barandiarán, J.M. and Hadjipanayis, G.C. and Palanisamy, D. and Schwarz, T. and Gault, B. and Raabe, D. and Skokov, K. and Gutfleisch, O. and Fischbacher, J. and Schrefl, T.

Volume: 200 Pages: 652-658
DOI: 10.1016/j.actamat.2020.08.075
Published: 2020

Recently 1:12 magnets of Sm-(Fe,V) have shown promising coercivities and the potential to be alternative rare-earth-lean permanent magnets. In this work, we investigated the effects of partial substitution of Cu, Mo and Ti for V in the magnets prepared by hot compaction and hot deformation of mechanically milled powders. The microstructure of the Sm-Fe-(V,Cu) and Sm-Fe-(V,Ti) hot-deformed magnets consisted in fine grains with sizes between 50 and 150 nm. The Sm-Fe-(V,Cu) magnet showed the best performance with μ0Hc=0.96 T, μ0Mr=0.49 T, (BH)max=42kJm−3 and TC=362∘C. Atom probe tomography of this magnet revealed the presence of a thin Sm17.5Fe71.5V8Cu3 intergranular phase of 3-6 nm surrounding the 1:12 nanograins. The addition of a small amount of Cu, not only improved the magnetic properties but also hindered the grain growth during hot deformation. Micromagnetic simulations of the magnetization reversal agreed with the experimental values of coercivity. The presence of the intergranular phase reduces the number of grains that switch simultaneously. © 2020 Acta Materialia Inc.

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