Shift in the absorption edge due to exchange in teraction in ferromagnetic semiconductors

Natalia Lebedeva, Pekka Kuivalainen

Research output: Contribution to journalArticleScientificpeer-review

2 Citations (Scopus)

Abstract

We develop the theory of the shift in the band edge caused by a strong exchange interaction between charge carrier spins and the spins of the localized magnetic electrons in ferromagnetic semiconductors.
The one-particle Green function is derived by using Matsubara's temperature Green functions, and then an infinite-order correction to the band edge due to the exchange interaction is determined from the poles of the Green function. With the aid of the temperature- and magnetic field-dependent spin polarization of the magnetic moments and the spin correlation functions, the band edge can be calculated as a function of temperature in various magnetic fields.
The calculated results are compared to experimental data in the cases of the ferromagnetic semiconductors EuO and Ga1-xMnxAs over a wide temperature range. For these materials the values 0.223 and 1.4 eV are evaluated for the exchange interaction parameter, respectively.
A new feature is found in the ferromagnetic region, as a result of the exceptionally strong exchange interaction in Ga1-xMnxAs, i.e., a blue-shift in the band edge with decreasing temperature or with increasing
Original languageEnglish
Pages (from-to)4491-4501
JournalJournal of Physics: Condensed Matter
Volume14
Issue number17
DOIs
Publication statusPublished - 2002
MoE publication typeA1 Journal article-refereed

Keywords

  • magnetic semiconductors
  • ferromagnetic materials
  • band gap blue shift
  • band shift

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