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3 Acta Physica Polonica A

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Magnetic Properties of Short Period InGaMnAs/InGaAs Superlattices

100%

Sadowski J. , Mathieu R. , Svedlindh P. , Kanski J. , Karlsteen M. , Świątek K. , Domagała J.

nr 4-5

687-694

We have observed a paramagnetic-to-ferromagnetic phase transition in short period InGaMnAs/InGaAs superlattices. The thicknesses of magnetic InGaMnAs layers in the structures studied was chosen to be 4 or 8 molecular layers (12Å or 24Å). The non-magnetic InGaAs spacer layers are 12Å thick. The composition (In content) in InGaMnAs and InGaAs was chosen in such a way that magnetic layers were: deep potential wells, high potential barriers, or shallow potential wells. For superlattices with 8 monolayer thick InGaMnAs magnetic layers and 4 monolayer thick InGaAs non-magnetic spacers the temperatures of paramagnetic-to-ferromagnetic phase transition do not depend on the band offsets between InGaMnAs and InGaAs adjusted by the In content.

Origin of Ultrafast Component of Photoluminescence Decay in Nanostructures Doped with Transition Metal or Rare-Earth Ions

84%

Godlewski M. , Yatsunenko S. , Ivanov V. , Khachapuridze A. , Świątek K. , Goldys E. , Phillips M. , Klar P. , Heimbrodt W.

nr 1

65-74

Bulk samples, layers, quantum well, and quantum dot structures of II-Mn-VI samples all show coexistence of slow and fast components of Mn^{2+} photoluminescence decay. Thus, fast photoluminescence decay cannot be related to low dimensionality of a host material. This also means that the model of the so-called quantum confined atom is incorrect. Based on the results of time-resolved photoluminescence and optically detected magnetic resonance investigations we relate the observed lifetime decrease in Mn^{2+} intra-shell transition to spin dependent magnetic interactions between localized spins of Mn^{2+} ions and between Mn^{2+} ions and spins/magnetic moments of free carriers. The latter mechanism is enhanced in nanostructures.

Ferromagnetic Transition in Ge_{1-x}Mn_{x}Te Layers

67%

Knoff W. , Domukhovski V. , Dybko K. , Dziawa P. , Jakieła R. , Łusakowska E. , Reszka A. , Świątek K. , Taliashvili B. , Story T. , Szałowski K. , Balcerzak T.

Acta Physica Polonica A

2009

tom 116

nr 5

904-906

Ferromagnetic transition temperature in thin layers of diluted magnetic (semimagnetic) semiconductor Ge_{1-x}Mn_{x}Te was studied experimentally by SQUID magnetometry method and analyzed theoretically for a model Ising-type diluted magnetic system with Ruderman-Kittel-Kasuya-Yosida indirect exchange interaction. The key features of the experimentally observed dependence of the Curie temperature on Mn content (x ≤ 0.12) and conducting hole concentration p = (1-10) × 10^{21} cm^{-3} were reproduced theoretically for realistic valence band and crystal lattice parameters of p-Ge_{1-x}Mn_{x}Te taking into account short carrier mean free path encountered in this material and Ruderman-Kittel-Kasuya-Yosida mechanism with both delta-like and diffused character of spatial dependence of the exchange coupling between magnetic ions and free carriers.