Biomedical subjects

H Ebert

Publications and source records attributed to H Ebert.

At least 19 recordsLinked to original sources

PubMed2006

Spectral function of ferromagnetic 3d metals: a self-consistent LSDA+DMFT approach combined with the one-step model of photoemission.

The electronic structure of ferromagnetic 3d-transition metals in the vicinity of the Fermi level is dominated by the spin-polarized d bands. Experimentally, this energy region can be probed in detail by means of angle-resolved ultraviolet photoemission and inverse photoemission. In several earlier studies the measured spectra were described either within a single-particle approach based on the local spin-density approximation including matrix-element effects within the so-called one-step model or by sophisticated many-body approaches neglecting these effects. In our analysis we combine for the first time correlation with matrix-element effects to achieve an improved interpretation of photoemission data from ferromagnetic nickel.

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PubMed2005

Experimental observation and theoretical description of the pure Fano effect in the valence-band photoemission of ferromagnets.

The pure Fano effect in angle-integrated valence-band photoemission of ferromagnets has been observed for the first time. A contribution of the intrinsic spin polarization to the spin polarization of the photoelectrons has been avoided by an appropriate choice of the experimental parameters. The theoretical description of the resulting spectra reveals a complete analogy to the Fano effect observed before for paramagnetic transition metals. While the theoretical photocurrent and spin-difference spectra are found in good quantitative agreement with experiment in the case of Fe and Co, only a qualitative agreement could be achieved in the case of Ni by calculations on the basis of plain local spin-density approximation. Agreement with experimental data could be improved in this case in a very substantial way by a treatment of correlation effects on the basis of dynamical mean field theory.

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PubMed2005

Psychological benefit of diagnostic certainty for mothers of children with disabilities: lessons from Down syndrome.

Diagnostic and prognostic uncertainty is one of the major psychological stressors for patients in acute and chronic illness, as well as for parents of children with disabilities or chronic disease. Whereas the parents' feeling of uncertainty is undoubtedly very strong shortly after the birth of a child with disabilities, the long-term effects on the parents of having or not having a precise genetic diagnosis, in terms of emotional stress, remain unclear. In this study, mothers of non-disabled children are compared to mothers of children with Down syndrome, and to mothers of children with a diagnostically unassigned mental retardation with regard to the level of anxiety, feelings of guilt, and emotional burden. While the mothers of children with Down syndrome score comparably to the mothers of non-disabled children, the results show broad psychoemotional disadvantages for mothers of children with a mental retardation of unknown etiology. Consequently, the value of genetic diagnosis of infantile disabilities encompasses, beyond clinical considerations like therapy planning and assignment of the recurrence risk for siblings, significant and long-lasting emotional relief for the parents.

Adult↗

PubMed2004

Direct observation of the multisheet Fermi surface in the strongly correlated transition metal compound ZrZn2.

The existence of flat areas of a Fermi surface (FS), predicted by electronic structure calculations and used in models of both magnetically mediated and phonon-mediated Fulde-Ferrell-Larkin-Ovchinnikov superconducting states, is reported in the paramagnetic phase of the ferromagnetic superconductor ZrZn2 using positron annihilation. The strongly mass-renormalized FS sheet, dominating the Fermi level density of states, is seen for the first time. The delocalization of the magnetization is studied using measured and calculated magnetic Compton profiles.

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PubMed2003

Field-induced magnetic circular x-ray dichroism in paramagnetic solids: a new magneto-optical effect.

It is demonstrated that for paramagnetic solids an external magnetic field-in analogy to the magneto-optical Kerr effect in the visible regime of light-gives rise to a magnetic circular dichroism in x-ray absorption (MCXD). A detailed description of this new field-induced magneto-optical phenomenon is given. In particular it is shown that the resulting dichroic spectra may be used to deduce the spin and orbital susceptibility in a component resolved way by making use of a modified form of the MCXD sum rules.

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PubMed2001

Strongly enhanced orbital moments and anisotropies of adatoms on the Ag(001) surface.

We present ab initio calculations for orbital moments and anisotropy energies of 3d and 5d adatoms on the Ag(001) surface, based on density functional theory, including Brooks' orbital polarization (OP) term, and applying a fully relativistic Korringa-Kohn-Rostoker-Green's function method. In general, we find unusually large orbital moments and anisotropy energies, e.g., in the 3d series, 2.57 mu(B) and +74 meV for Co, and, in the 5d series, 1.78 mu(B) and +42 meV for Os. These magnetic properties are determined mainly by the OP and even exist without spin-orbit coupling.

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PubMed2000

Layer-resolved magnetic moments in Ni/Pt multilayers

The magnetic moments in Ni/Pt multilayers are thoroughly studied by combining experimental and ab initio theoretical techniques. SQUID magnetometry probes the samples' magnetizations. X-ray magnetic circular dichroism separates the contribution of Ni and Pt and provides a layer-resolved magnetic moment profile for the whole system. The results are compared to band-structure calculations. Induced Pt magnetic moments localized mostly at the interface are revealed. No magnetically "dead" Ni layers are found. The magnetization per Ni volume is slightly enhanced compared to bulk NiPt alloys.

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PubMed1999