Femtosecond laser excitations in half-metal (HM) compounds are theoretically predicted to induce ... more Femtosecond laser excitations in half-metal (HM) compounds are theoretically predicted to induce an exotic picosecond spin dynamics. In particular, conversely to what is observed in conventional metals and semiconductors, the thermalization process in HMs leads to a long living partially thermalized configuration characterized by three Fermi-Dirac distributions for the minority, majority conduction, and majority valence electrons respectively. Remarkably, these distributions have the same temperature but different chemical potentials. This unusual thermodynamic state is causing a persistent non-equilibrium spin polarization only well above the Fermi energy. Femtosecond spin dynamics experiments performed on Fe3O4 by time-and spin-resolved photoelectron spectroscopy are support on our model. Furthermore, the spin polarization response proves to be very robust and it can be adopted to selectively test the bulk HM character in a wide range of compounds.
ABSTRACT Mn 5 Ge 3 (001) thin films grown on Ge (111) were studied by angle-and spin-resolved pho... more ABSTRACT Mn 5 Ge 3 (001) thin films grown on Ge (111) were studied by angle-and spin-resolved photoemission using synchrotron radiation in the 17 – 40 eV photon energy range. The photoelectron spectra were simulated starting from a first-principles band-structure calculation for the ground state , using the free-electron approximation for the final states , taking into account photohole lifetime effects and k ⊥ broadening plus correlation effects , but ignoring transition matrix elements. The measured spin polarizations for the various k points investigated in the MLA plane of the Brillouin zone are found to be in fair enough agreement with the simulated ones , providing a strong support to the ground-state band-structure calculations. Possible origins for the departures between either simulations and experiments or previous and present experiments are discussed .
We have performed angle-and spin-resolved photoemission measurements on Fe 3 O 4 (0 0 1)/MgO(0 0 ... more We have performed angle-and spin-resolved photoemission measurements on Fe 3 O 4 (0 0 1)/MgO(0 0 1). Despite intrinsic electron-lattice (polaron) interaction a Fe t 2g band dispersion is observed, as well as a Fermi surface. The states close to the Fermi level show a spin polarization up to −72% as measured with a 4.65 eV laser light. All the data can be simulated starting from GGA + U bulk band-structure calculations and taking into account the polaron and initial-state lifetime broadening involved in the photoemission process. This conciliates the electronic structure of Fe 3 O 4 with a band model and confirms the half-metallic nature of Fe 3 O 4 .
Mn 5 Ge 3 (001) thin films grown on Ge(111)-c(2 × 8) reconstructed surfaces were studied by angle... more Mn 5 Ge 3 (001) thin films grown on Ge(111)-c(2 × 8) reconstructed surfaces were studied by angle-resolved photoemission using synchrotron radiation in the 14-94 eV photon energy range. The results obtained in the ALM plane and in the AHK plane are in agreement with simulations starting with band structure calculations based on the density functional theory. This provides a unique validation of band structure calculations for a proper description of the electronic properties of Mn 5 Ge 3 . Only the spectral feature very close to the Fermi level cannot be well explained by the simulation. This departure is discussed in terms of the three-dimensional nature of the sample and of correlation effects.
Femtosecond laser excitations in half-metal (HM) compounds are theoretically predicted to induce ... more Femtosecond laser excitations in half-metal (HM) compounds are theoretically predicted to induce an exotic picosecond spin dynamics. In particular, conversely to what is observed in conventional metals and semiconductors, the thermalization process in HMs leads to a long living partially thermalized configuration characterized by three Fermi-Dirac distributions for the minority, majority conduction, and majority valence electrons respectively. Remarkably, these distributions have the same temperature but different chemical potentials. This unusual thermodynamic state is causing a persistent non-equilibrium spin polarization only well above the Fermi energy. Femtosecond spin dynamics experiments performed on Fe3O4 by time-and spin-resolved photoelectron spectroscopy are support on our model. Furthermore, the spin polarization response proves to be very robust and it can be adopted to selectively test the bulk HM character in a wide range of compounds.
ABSTRACT Mn 5 Ge 3 (001) thin films grown on Ge (111) were studied by angle-and spin-resolved pho... more ABSTRACT Mn 5 Ge 3 (001) thin films grown on Ge (111) were studied by angle-and spin-resolved photoemission using synchrotron radiation in the 17 – 40 eV photon energy range. The photoelectron spectra were simulated starting from a first-principles band-structure calculation for the ground state , using the free-electron approximation for the final states , taking into account photohole lifetime effects and k ⊥ broadening plus correlation effects , but ignoring transition matrix elements. The measured spin polarizations for the various k points investigated in the MLA plane of the Brillouin zone are found to be in fair enough agreement with the simulated ones , providing a strong support to the ground-state band-structure calculations. Possible origins for the departures between either simulations and experiments or previous and present experiments are discussed .
We have performed angle-and spin-resolved photoemission measurements on Fe 3 O 4 (0 0 1)/MgO(0 0 ... more We have performed angle-and spin-resolved photoemission measurements on Fe 3 O 4 (0 0 1)/MgO(0 0 1). Despite intrinsic electron-lattice (polaron) interaction a Fe t 2g band dispersion is observed, as well as a Fermi surface. The states close to the Fermi level show a spin polarization up to −72% as measured with a 4.65 eV laser light. All the data can be simulated starting from GGA + U bulk band-structure calculations and taking into account the polaron and initial-state lifetime broadening involved in the photoemission process. This conciliates the electronic structure of Fe 3 O 4 with a band model and confirms the half-metallic nature of Fe 3 O 4 .
Mn 5 Ge 3 (001) thin films grown on Ge(111)-c(2 × 8) reconstructed surfaces were studied by angle... more Mn 5 Ge 3 (001) thin films grown on Ge(111)-c(2 × 8) reconstructed surfaces were studied by angle-resolved photoemission using synchrotron radiation in the 14-94 eV photon energy range. The results obtained in the ALM plane and in the AHK plane are in agreement with simulations starting with band structure calculations based on the density functional theory. This provides a unique validation of band structure calculations for a proper description of the electronic properties of Mn 5 Ge 3 . Only the spectral feature very close to the Fermi level cannot be well explained by the simulation. This departure is discussed in terms of the three-dimensional nature of the sample and of correlation effects.
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