Alexander B. Shick

IMPLEMENTATION OF THE LDA+U METHOD USING THE FULL-POTENTIAL LINEARIZED AUGMENTED PLANE-WAVE BASIS

We provide a straightforward and efficient procedure to combine the local density approximation plus Hubbard U (LDA+U) total-energy functional with the full-potential linearized augmented plane-wave method. A detailed derivation of the LDA+U Kohn-Sham-type equations is presented for the augmented plane-wave basis set, and a simple ``second-variation-based procedure for self-consistent LDA+U calculations is given. The method is applied to calculate the electronic structure and magnetic properties of NiO and Gd. The magnetic moments and band eigenvalues obtained are in very good quantitative agreement with previous full-potential linear muffin-tin orbital calculations. We point out that LDA+U reduces the total d charge on Ni by 0.1 in NiO.

SUPERCONDUCTIVITY IN FERROMAGNETIC RUSR2GDCU2O8

Relying on the inhomogeneous (layered) crystal, electronic, and magnetic structure, we show how superconductivity can coexist with the ferromagnetic phase of RuSr2GdCu2O8 as observed by Tallon and coworkers. Since the Cu d_{x^2-y^2} orbitals couple only to apical O p_x, p_y orbitals (and only weakly), which also couple only weakly to the magnetic Ru t_{2g} orbitals, there is sufficiently weak exchange splitting, especially of the symmetric CuO2 bilayer Fermi surface, to allow singlet pairing. The exchange splitting is calculated to be large enough that the superconducting order parameter may be of the Fulde-Ferrell-Larkin-Ovchinnikov type. We also note that pi-phase formation is preferred by the magnetic characteristics of RuSr2GdCu2O8.

Magnetism, spin-orbit coupling, and superconducting pairing in UGe2.

A consistent picture on the mean-field level of the magnetic properties and electronic structure of the superconducting itinerant ferromagnet UGe2 requires inclusion of correlation effects beyond the local density approximation (LDA). The LDA+U approach reproduces both the magnitude of the observed moment and the magnetocrystalline anisotropy. The largest Fermi surface sheet is composed primarily of spin majority states with orbital projection m(l) = 0, suggesting a much simpler picture of the pairing than is possible for general strong spin-orbit coupled materials. The quasi-two-dimensional geometry of the Fermi surface supports the likelihood of magnetically mediated p-wave triplet pairing.

Electronic Structure and Nonmagnetic Character of Delta-Pu-Am Alloys

The around-mean-field LSDA+U correlated band theory is applied to investigate the electronic and magnetic structure of fcc-Pu-Am alloys. Despite a lattice expansion caused by the Am atoms, neither ...

Ground and metastable states in γ-Ce from correlated band theory

Abstract The effects of electron correlation on the electronic structure and spin and orbital magnetic properties of the f.c.c. Ce were investigated using the relativistic (with spin–orbit coupling included) full-potential linearized augmented plane wave implementation of correlated band theory (‘LDA+U’). Multiple energy minima of the LDA+U energy functional are obtained for γ-Ce. The lowest energy solution leads to a fully spin polarized 4f state and the lattice constant of γ-Ce. The higher energy local minima (additional self-consistent solutions) are shown to be strongly indicative of low-energy excitations.

Multiplet effects in the electronic structure of δ-Pu, Am and their compounds

We propose a straightforward and efficient procedure to perform dynamical mean-field (DMFT) calculations on the top of the static mean-field LDA+U approximation. Starting from self-consistent LDA+U ground state we included multiplet transitions using the Hubbard-I approximation, which yields a very good agreement with experimental photoelectron spectra of δ-Pu, Am, and their selected compounds.

Electron correlation effects and magnetic ordering at the Gd(0001) surface

Effects of electron correlation on the electronic structure and magnetic properties of the Gd(0001) surface are investigated using the full-potential linearized augmented plane-wave implementation of correlated band theory (LDA+U). The use of LDA+U instead of LDA (local-density approximation) total-energy calculations produces the correct ferromagnetic ground state for both bulk Gd and the Gd surface. Surface strain relaxation leads to a 90% enhancement of the interlayer surface-to-bulk effective exchange coupling. Application of a Landau-Ginzburg-type theory yields a 30% enhancement of the Curie temperature at the surface, in very good agreement with the experiment. (c) 2000 The American Physical Society.

FIRST-PRINCIPLES CALCULATION OF UNIAXIAL MAGNETIC ANISOTROPY AND MAGNETOSTRICTION IN STRAINED COLOSSAL MAGNETORESISTANCE FILMS

We performed first - principles relativistic full-potential linearized augmented plane wave calculations for strained tetragonal ferromagnetic La(Ba)MnO

Anomalous ferromagnetism of a monatomic Co wire at the Pt(111) surface step edge

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Relationship of tunnelling magnetoresistance and buried-layer densities of states as derived from standing-wave excited photoemission

with an assumed experimental structure of thin strained tetragonal La