| 1. |
- Rönnow, Daniel, et al.
(författare)
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Isotope effects on the electronic critical points of germanium : Ellipsometric investigation of the E1 and E1+ Delta(1) transitions
- 1998
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Ingår i: European Physical Journal B. - : Springer Science and Business Media LLC. - 1434-6028 .- 1434-6036. ; 5:1, s. 29-35
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Tidskriftsartikel (refereegranskat)abstract
- Within the past years the optical excitations of electrons have been measured for semiconductor samples of different isotope compositions. The isotope shift observed have been compared with calculations of the effects of electron-phonon interaction on the electronic band structure. While qualitative agreement has been obtained, some discrepancies remain especially concerning the E1 and E1 + Delta(1) transitions. We have remeasured the effect of isotope mass on the E1 and E1 + Delta(1) transitions of germanium with several isotopic compositions. The results, obtained by means of spectroscopic ellipsometry, confirm that the real part of the gap self-energies induced by electron-phonon interaction is larger than found from band structure calculations, while the imaginary part agrees with those calculations, which are based on a pseudopotential band structure and a bond charge model for the lattice dynamics. Our results agree with predictions based on the measured temperature dependence of the gaps. We compare our data for E1 and E1 + Delta(1) with results for the lowest direct (E0) and indirect (E9) gaps. The measured values of Δ0 and Δ1 increase noticeably with increasing isotope mass. Similar effects have been observed in the temperature dependence of Delta(1) in alpha-Sn and GaSb. A microscopic explanation for this effect is not available.
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| 2. |
- Djurberg, C, et al.
(författare)
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Magnetic relaxation phenomena in a CuMn spin glass
- 1999
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Ingår i: EUROPEAN PHYSICAL JOURNAL B. - : SPRINGER VERLAG. - 1434-6028. ; 10:1, s. 15-21
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Tidskriftsartikel (refereegranskat)abstract
- Experiments on the temperature and time dependence of the response function and the field cooled magnetisation of a Cu(Mn) spin glass at temperatures below the zero field spin glass temperature are used to explore the non-equilibrium nature of the underly
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| 3. |
- Garcia-Palacios, JL
(författare)
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Brownian rotation of classical spins: dynamical equations for non-bilinear spin-environment couplings
- 1999
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Ingår i: EUROPEAN PHYSICAL JOURNAL B. - : SPRINGER VERLAG. - 1434-6028. ; 11:2, s. 293-308
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Dynamical equations for a classical spin interacting with the surrounding medium are derived by means of the formalism of the oscillator-bath environment. The bilinear-coupling treatment of Jayannavar (Z. Phys. B 82, 153 (1991)) is extended to couplings t
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| 4. |
- Jonason, K, et al.
(författare)
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Sensitivity to temperature perturbations of the aging states in a re-entrant ferromagnet
- 1999
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Ingår i: EUROPEAN PHYSICAL JOURNAL B. - : SPRINGER VERLAG. - 1434-6028. ; 10:1, s. 23-28
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic magnetic properties and ageing phenomena of the re-entrant ferromagnet (Feo.Ni-20(0.80))(75)P16B6Al3 are investigated by time dependent zero field cooled magnetic relaxation, m(t), measurements. The influence of a temperature cycling (perturbation
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