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Electric polarization

Spin magnetism. Lattice displacements. Electric polarization. Orbital magnetism. Magnetoelectric Coupling in Cr 2 O 3 David H. Vanderbilt, Rutgers University New Brunswick, DMR 1005838.

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Electric polarization

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  1. Spin magnetism Lattice displacements Electric polarization Orbital magnetism Magnetoelectric Coupling in Cr2O3David H. Vanderbilt, Rutgers University New Brunswick, DMR 1005838 For certain insulating crystals, it is possible for the electrical and magnetic properties to be coupled via a mechanism known as magnetoelectricity. In such crystals, an applied electric field induces a magnetization, and conversely, an applied magnetic field induces an electric polarization. Cromium oxide (Cr2O3) was predicted to exhibit this effect based on its symmetry in 1959, and the first experimental measurements of the magnetoelectric coupling coefficients appeared in the early 1960s. Ever since, it has been a model system for the study of magnetoelectricity. However, a complete theory of the magnetoelectric coupling in this material was missing, because such a theory must cover: • Five separate contributions to the magnetoelectric coupling, indicated by the double arrows at right, all of which need to be calculated. • Methods for computing the direct coupling between electric polarization and orbital magnetism were only recently developed under this NSF-sponsored work. Magnetoelectric coupling. Electrical properties can be connected to magnetic properties either directly (green double arrows) or via lattice displacements (blue double arrows). Magnetic properties come in two flavors: spin (top) and orbital (bottom). We computed all of these couplings from first principles for Cr2O3. We have now carried out a complete calculation of this kind for Cr2O3, quantifying the relative importance of the various contributions for the first time.

  2. Magnetoelectric Coupling in Cr2O3David H. Vanderbilt, Rutgers University New Brunswick, DMR 1005838 http://www.physics.rutgers.edu/~dhv/uspp Broader impacts: • Web sites maintained for general community use (see at right): • Ultrasoft Pseudopotentials • Wannier 90 • Contributions to open-source software packages • ABINIT • PWSCF (Quantum Espresso) • Service on scientific committees for international conferences including: • 15th International Workshop on Computational Physics and Materials Science, Trieste, Italy, 13-15 January, 2011 • Co-organizer, CECAM Workshop on Topological Insulators and Non-Perturbative Spin-Orbit Coupling, Lausanne, Switzerland, Jan. 9-11, 2012. USPP: Software for generating ultrasoft pseudopotentials, and library of input files for most elements in the periodic table. http://www.wannier.org Wannier90: Software for constructing maximally localized Wannier functions (with A.A. Mostofi, J.R. Yates, Y.-S. Lee, I. Souza, and N. Marzari)

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