Giant Magnetic Anisotropy in Metastable FePt Alloy

다국어 초록 (Multilingual Abstract)

As information storage and high-speed permanent magnet motor technologies have evolved, high-performance permanent magnetic materials with large saturation magnetization and magnetic anisotropy (MA) become indispensable. In this presentation, we report results of first-principles calculations on structural and intrinsic magnetic properties of L10-ordered FePt alloy along the so-called Bain path. Our total energy calculations reveal that the body centered tetragonal (bct) structure of FePt with c/a=0.85 is identified as a metastable phase, which can be epitaxially grown on an appropriate substrate. More remarkably, both saturation magnetization and uniaxial MA of this bct metastable phase are significantly larger compared with those of the ground state L10-FePt and other known magnetic materials. Single-particle energy spectrum analyses indicate that while the Pt 5d orbital states determine the MA-driven permanent magnetic properties in L10-FePt alloy, the large enhancement of MA in the metastable structure mainly originates from the Fe 3d orbital states. We will also discuss our more recent findings on possibilities of further improving the performance of the metastable permanent magnet FePt with a series of 3d and 4d transition metal dopant elements.