Reichel L, Schultz L, Pohl D, Oswald S, Fähler S, Werwiński M, Edström A, Delczeg-Czirjak E K, Rusz J
IFW Dresden, 01171 Dresden, Germany. Faculty of Mechanical Engineering, Institute of Materials Science, TU Dresden, 01062 Dresden, Germany.
J Phys Condens Matter. 2015 Dec 2;27(47):476002. doi: 10.1088/0953-8984/27/47/476002. Epub 2015 Nov 9.
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.
为了将广为人知的Fe-Co-B合金从软磁体转变为硬磁体，我们提出通过间隙硼引入四方应变。密度泛函理论表明，当B原子占据八面体间隙位置时，体心立方Fe-Co晶格会自发应变。预计这种高度畸变的Fe-Co会达到很强的磁晶各向异性，它可能与形状各向异性相抗衡。为了通过实验探究这一理论推测，我们对外延薄膜进行了研究。对于硼含量高达4原子百分比的情况，可获得高达5%晶格畸变的自发应变，这导致单轴各向异性常数超过0.5兆焦每立方米。然而，进一步添加硼会导致部分非晶化，这会使各向异性和磁化强度都降低。
