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arXiv · 1509.04126

From soft to hard magnetic Fe-Co-B by spontaneous strain: A combined first principle and thin film study

Ludwig Reichel·Ludwig Schultz·Darius Pohl·Steffen Oswald·Sebastian Fähler·Miroslaw Werwinski·Alexander Edström·Erna K. Delczeg-Czirjak·Jan Rusz
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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. Probing this theoretical suggestion experimentally, epitaxial films are examined. A spontaneous strain up to 5 % lattice distortion is obtained for B contents 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 amorphization, which degrades both anisotropy and magnetization.

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Ludwig Reichel, Ludwig Schultz, Darius Pohl, Steffen Oswald, Sebastian Fähler, Miroslaw Werwinski, Alexander Edström, Erna K. Delczeg-Czirjak, Jan Rusz. 2015-09-14. From soft to hard magnetic Fe-Co-B by spontaneous strain: A combined first principle and thin film study. https://doi.org/10.1088/0953-8984%2F27%2F47%2F476002

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