From soft to hard magnetic Fe–Co–B by spontaneous strain: a combined first principles and thin film study. (9th November 2015)

• Record Type: Journal Article
• Authors: Reichel, L; Schultz, L; Pohl, D; Oswald, S; Fähler, S; Werwiński, M; Edström, A; Delczeg-Czirjak, E K; Rusz, J
• Is Part Of: Journal of physics. Volume 27:Number 47(2015)
• Publication Date: 2015-11-09
• Subjects: Fe–Co -- rare-earth free permanent magnet -- magnetocrystalline anisotropy -- tetragonal strain -- DFT; Condensed matter -- Periodicals; Matière condensée -- Périodiques; Vaste stoffen; Vloeistoffen; Natuurkunde; Electronic journals; Computer network resources; 530.4105
• DOI: 10.1088/0953-8984/27/47/476002
• Languages: English
• ISSNs: 0953-8984

Abstract

Abstract: In order to convert the well-known Fe–Co–B alloy from a soft to a hard magnet, we propose tetragonal strain by interstitial boron. Density functional theory reveals that when B atoms occupy octahedral interstitial sites, the bcc Fe–Co lattice is strained spontaneously. Such highly distorted Fe–Co is predicted to reach a strong magnetocrystalline anisotropy which may compete with shape anisotropy. To probe this theoretical suggestion experimentally, epitaxial films are examined. A spontaneous strain up to 5% lattice distortion is obtained for B content up to 4 at%, which leads to uniaxial anisotropy constants exceeding 0.5 MJ m −3 . However, a further addition of B results in a partial amorphisation, which degrades both anisotropy and magnetisation.