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Inelastic Scattering and Spin Polarization in Dilute Magnetic Semiconductor (Ga,Mn)Sb

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 Publication date 2007
  fields Physics
and research's language is English




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The Point Contact Andreev Reflection (PCAR) technique has already been used to measure the spin polarization of some of the dilute magnetic semiconductors, such as narrow-band (In,Mn)Sb, as well as wider gap (Ga,Mn)As. While in (In,Mn)Sb conventional Andreev reflection has been demonstrated, in (Ga,Mn)As quasiparticle density of states (DOS) broadening has been observed, possibly due to inelastic scattering effects. Here, we investigate the spin polarization, magnetic, and transport properties of epitaxially grown (Ga,Mn)Sb films with the Curie temperature of ~ 10K. The spin polarization of 57+/-5% was measured. Spectrum broadening in (Ga,Mn)Sb has also been observed.

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We report here first extensive measurements of the temperature dependence of phonon density of states of BaFe2As2, the parent compound of the newly discovered FeAs-based superconductors, using inelastic neutron scattering. The experiments were carried out on the thermal time-of-flight neutron spectrometer IN4 at the ILL on a polycrystalline sample. There is no appreciable change in the spectra between T = 10 K and 200 K, although the sample undergoes a magnetic as well as a tetragonal-to-orthorhombic structural phase transition at 140 K. This indicates a rather harmonic phonon system. Shell model lattice dynamical calculations based on interatomic potentials are carried out to characterize the phonon data. The calculations predict a shift of the Ba-phonons to higher energies at 4 GPa. The average energy of the phonons of the Ba-sublattice is also predicted to increase on partial substitution of Ba by K to Ba0.6K0.4. The calculations show good agreement with the experimental phonon spectra, and also with the specific heat data from the literature.
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