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Magneto-transport Properties of Fe Thin Films in an External Electric Field
K. Nakamura,T. Akiyama,T. Ito,M. Weinert,A. J. Freeman 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
Magneto-transport properties in Fe thin films in an external electric field (E-field) were investigatedby means of the first-principles full-potential linearized augmented plane-wave method. Results for an Fe monolayer predict a reduction (enhancement) in the in-plane dc electric (intrinsicHall) conductivity due to a change in the band structure around the Fermi energy when the E-fieldis introduced. In addition, a magnetization reorientation from the out-of-plane direction to thein-plane direction leads to an abrupt change in the conductivity. Modification of the ac electricconductivity by an E-field is also presented.
K. Nakamura,T. Akiyama,T. Ito,M. Weinert,A. J. Freeman 한국자기학회 2011 Journal of Magnetics Vol.16 No.2
We report results of first principles calculations for effects of an external electric field (E-field) on the magnetocrystalline anisotropy (MCA) in transition-metal (Fe, Co, and Ni) monolayers and at metal-insulator (Fe/MgO) interfaces by means of full-potential linearized augmented plane wave method. For the monolayers, the MCA in the Fe monolayer (but not in the Co and Ni) is modified by the E-field, and a giant modification is achieved in the Fe0.75Co0.25. For the Fe/MgO interfaces, the ideal Fe/MgO interface gives rise to a large out-ofplane MCA, and a MCA modification is induced when an E-field is introduced. However, the existence of an interfacial FeO layer between the Fe layer and the MgO substrate may play a key role in demonstrating an Efield-driven MCA switching, i.e., from out-of-plane MCA to in-plane MCA.
Seung-Woo Seo,You Young Song,Gul Rahman,In Gee Kim,M. Weinert,A. J. Freeman 한국자기학회 2009 Journal of Magnetics Vol.14 No.4
The convergence behavior of the all-electron full-potential linearized augmented plane-wave (FLAPW) method with the explicit orthogonalization (XO) scheme is tested on ferromagnetic bulk body-centered-cubic Fe. Applying a commonly used criterion relating the plane-wave and angular momentum cutoffs, lmax = RMTKmax, where RMT is the muffin-tin (MT) sphere radius and Kmax is the plane-wave cutoff for the basis ? the total energy is converged and stable for KmaxRMT = 10. The total energy convergence dependence on the star-function cutoff, Gmax, is minimal and so a Gmax of 3Kmax or a large enough Gmax is a reasonable choice. We demonstrate that the convergence with respect to lmax or a fixed large enough Gmax and Kmax are independent, and that Kmax provides a better measure of the convergence than RMTKmax. The dependence of the total energy on RMT is shown to be small if the core states are treated equivalently, and that the XO scheme is able to treat systems with significantly smaller RMT than the standard LAPW method. For converged systems, the calculated lattice parameter, bulk modulus, and magnetic moments are in excellent agreement with the experimental values.
Magnetism and Multiplets in Fe-phthalocyanine Molecules
Yukie Kitaoka,Kohji Nakamura,Toru Akiyama,Tomonori Ito,M. Weinert,A. J. Freeman 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
Magnetism and multiplets for Fe-phthalocyanine molecules were investigated based on the constraintdensity functional theory (DFT) by imposing a density matrix constraint on the d-orbitaloccupation numbers. We demonstrate that for a single FePc molecule, there are three stationarystates of multiplets, 3Eg, 3A2g, and 3B2g, and that the magnetic anisotropy (MA) strongly dependson the multiplet structures. The ground state of the 3A2g obtained from the constraint DFT totalenergy calculations has planar MA, with the spin moments pointing along the molecule’s planardirection. The columnar stacking structure for α-FePc, with the ground state of the 3Eg, showsplanar MA.