D. Paudyal, C. Bhandari, M.E. Flatté
Ames National Laboratory,
Keywords: permanent magnets, magnetic anisotropy, hexaferrites
Summary:Enhanced magnetic anisotropy in lanthanum M-type hexaferrites by quantum-confined charge transfer Durga Paudyal, 1,2 Churna Bhandari, 1 and Michael E. Flatté, 3 1The Critical Materials Institute, Ames National Laboratory, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA 2Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa 50011, USA 3Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242, USA Iron-based hexaferrites are critical-element-free permanent magnet components of magnetic devices. Of particular interest is electron-doped M-type hexaferrite i.e., LaFe12O19 (LaM) in which extra electrons introduced by lanthanum substitution of barium/strontium play a key role in uplifting the magneto-crystalline anisotropy. We investigate the electronic structure of lanthanum hexaferrite using a density functional theory with localized charge density, which reproduces semiconducting behavior and identifies the origin of the very large magneto-crystalline anisotropy. Localized charge transfer from lanthanum to the iron at the crystal’s 2a site produces a narrow 3dz2 valence band strongly locking the magnetization along the c-axis. The calculated uniaxial magnetic anisotropy energies from fully self-consistent calculations are nearly double the single-shot values, and agree well with available experiments. The chemical similarity of lanthanum to other rare earths suggests that LaM can host other rare earths possessing nontrivial 4f electronic states to further enhance magnetic anisotropy critically needed for permanent magnets. This work is supported by the Critical Materials Institute, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office. The Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University of Science and Technology under Contract No. DE-AC02-07CH11358.