The electronic structure of the first reported heavy fermion compound without f electrons, LiV 2 O 4 , was studied by an ab initio calculation method. As a result of the trigonal splitting and d-d Coulomb interaction, one electron of the d 1.5 configuration of the V ion is localized and the rest partially fills a relatively broad conduction band. The effective Anderson impurity model was solved by the noncrossing-approximation method, leading to an estimation for the single-site Kondo energy scale T K . Then, we show how the so-called exhaustion phenomenon of Nozières for the Kondo lattice leads to a remarkable decrease of the heavy-fermion (or coherence) energy scale T coh ϵ T 2 K ͞D (D is the typical bandwidth), comparable to the experimental result.

We have calculated ground state properties and excitation spectra for Ce metal with the ab initio computational scheme combining local density approximation and dynamical mean-field theory (LDA+DMFT). We considered all electronic states, i.e. correlated f -states and non-correlated s-, p-and d-states. The strong local correlations (Coulomb interaction) among the f -states lead to typical many-body resonances in the partial f -density, such as lower and upper Hubbard band. Additionally the well known Kondo resonance is observed. The s-, p-and d-densities show small to mediate renormalization effects due to hybridization. We observe different Kondo temperatures for α-and γ-Ce (TK,α ≈ 1000 K and TK,γ ≈ 30 K), due to strong volume dependence of the effective hybridization strength for the localized f -electrons. Finally we compare our results with a variety of experimental data, i.e. from photoemission spectroscopy (PES), inverse photoemission spectroscopy (BIS), resonant inverse photoemission spectroscopy (RIPES) and magnetic susceptibility measurements.71.27.+a Strongly correlated electron systems , 74.25.Jb Electronic structure Ce metal is the simplest lanthanide compound with only one atom in a face centered cubic (fcc) crystal structure and a relatively small set of relevant electronic states derived from s-, p-d-and f -orbitals of Ce. It shows an unique isostructural (fcc to fcc) α → γ phase transition with increasing temperature. The high-temperature γ phase has 15% larger volume and displays a Curie-Weiss-like temperature dependence of the magnetic susceptibility signaling the existence of local magnetic moments while the α-phase has a Pauli-like temperature independent paramagnetism [1].While many different models were proposed to describe this system (for a review see [2]), the most relevant seems to be the periodic Anderson model. Studies based on the single impurity Anderson model [3] with a hybridization function obtained from LDA band structure calculations were rather successful in reproducing Kondo scales and spectra for α-and γ-Ce. However, an empirical renormalization of the hybridization function and position of the impurity level were needed for satisfactory agreement between calculated and experimental spectra.Due to the recent development of the Dynamical Mean-Field Theory [4] a more realistic treatment of Ce is now possible. In contrast to the Hubbard model (degenerate and non-degenerate), where hybridization occurs only between correlated d-or f -orbitals, Ce is much more complicated. The direct f -f hybridization is of the same order of magnitude as the hybridization of f -orbitals with the delocalized spd-states. Thus in order to describe Ce one even has to go beyond the periodic Anderson model, where only hybridization of the correlated f -orbitals with the delocalized states is included. In order to address this problem we used the most general procedure for calculating the Green function using a full basis set (s, p, d, f ) Hamiltonian with the integration over Brillouin zone in k-space....

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Epitaxial Fe34Co66 films in a thickness range from 3 to 100 monolayers (MLs) were grown by molecular beam epitaxy on GaAs(001) at room temperature. The growth was characterized by reflection high energy electron diffraction and x-ray diffraction. The magnetic properties were investigated by alternating gradient magnetometry magneto-optic Kerr effect, and superconducting quantum interference device magnetometry. The films show a strong interface-induced uniaxial in-plane anisotropy with the easy axis along [110]. In addition, the fourfold anisotropy coefficient changes sign around 6 ML i.e., the easy axis of the fourfold anisotropy switches from 〈110〉 to 〈100〉 with decreasing thickness.