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1
Content available remote Spectral dependence of magnetooptical Kerr effect in EuS-based ferromagnetic semiconductor multilayers
Szot M., Kowalczyk L., Smajek E., Volobuev V. V., Sipatov A. Y., Story T.
Materials Science Poland
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2008
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Vol. 26, No. 4
1033--1037
EN
The magnetooptical Kerr effect (MOKE) magnetometry was used to study the magnetic hysteresis loops of EuS-PbS and EuS-SrS semiconductor epitaxial multilayers composed of ferromagnetic layers of EuS and nonmagnetic ultrathin spacer layers of PbS or SrS. The spectral dependence of the MOKE in EuS-based semiconductor multilayers was studied in the photon energy range covering the fundamental interband electronic transitions in EuS. The measurements of the longitudinal MOKE established two maxima on the spectral dependence of the Kerr rotation for the photon energy hν = 1.65 eV and hν = 2.1 eV. This experimental finding is explained based on the model of the electronic band structure of EuS. The observed maxima of the Kerr rotation correspond to the electronic transitions from the localized 4f levels of Eu2+ ions and from 3p valence band to the 5d-6s conduction band of EuS. Spectral dependence of magnetooptical Kerr effect in EuS-based ferromagnetic semiconductor multilayers.
2
Content available remote Magnetic properties of silicon crystals implanted with manganese
Osinniy V., Misiuk A., Szot M., Świątek K., Bąk-Misiuk J., Barcz A., Jung W., Prujszczyk M., Story T.
Materials Science Poland
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2008
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Vol. 26, No. 3
751--757
EN
The influence of thermal treatment on magnetic properties of Si/Mn crystals grown by the Czochralski and by floating zone methods and implanted with Mn+ ions was studied by the SQUID magnetometry and electron spin resonance. Depending on thermal and hydrostatic pressure annealing conditions, three groups of Si/Mn samples were found: samples with only ferromagnetic phase, samples with ferromagnetic and paramagnetic contributions, and diamagnetic samples. The Curie temperature of ferromagnetic phase exceeds room temperature. The ESR and SQUID measurements suggest that Si/Mn implanted layer is magnetically inhomogeneous.
3
Content available remote Ferromagnetic and structural properties of Ge1-xMnxTe epitaxial layers
Knoff W, Dziawa P, Osinniy V, Taliashvili B, Domuchowski W, Diduszko R, Domagała J, Łusakowska E, Jakieła R, Story T
Materials Science Poland
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2008
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Vol. 26, No. 4
295--300
EN
Magnetic properties of thin layers of p-Ge1–xMnxTe (x < 0.2) semimagnetic (diluted magnetic) semiconductor exhibiting carrier induced ferromagnetism were experimentally studied. The layers were grown on BaF2 (111) substrates by molecular beam epitaxy technique. X-ray diffraction analysis performed at room temperature revealed monocrystalline (111)-oriented rhombohedral (exhibiting ferroelectric properties) crystal structure of Ge1–xMnxTe layers in the entire range of Mn content studied. The examination of the magnetic properties of the layers carried out by superconducting SQUID magnetometry and ferromagnetic resonance technique showed the ferromagnetic transition with the Curie temperature in the range 10–100 K depending on the Mn content and the hole concentration. Contrary to polycrystalline GeMnTe layers, it was experimentally found that in monocrystalline layers of GeMnTe an easy magnetization axis is directed along a normal to the layer plane. This effect is discussed in terms of strain present in these layers due to thermal expansion coefficients mismatch between the substrate and the GeMnTe layer.
4
Content available remote Photoemission study of Eu 2+/3+ ions in ferromagnetic (Eu,Gd)Te semiconductor layers
Dziawa P., Orłowski B. A., Osinniy V., Pietrzyk M., Taliashvili B., Story T., Johnson R. L.
Materials Science Poland
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2007
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Vol. 25, No. 2
377--382
EN
(Eu,Gd)Te ferromagnetic semiconductor layers grown by molecular beam epitaxy technique on BaF2 (111) monocrystalline substrates were investigated by resonant photoemission spectroscopy using synchrotron radiation. In n-(Eu,Gd)Te layers, a ferromagnetic transition induced by electron concentration is observed. Magnetic as well as electrical properties of this material depend strongly on the charge state (2+ vs. 3+) of Eu and Gd ions known to be sensitive to crystal stoichiometry and formation of oxide complexes. The relative concentration of Eu2+ and Eu3+ ions was determined from the analysis of the resonant photoemission energy distribution curves (EDC), measured at photon energies close to 4d-4f resonance. After various in-situ annealing and Ar sputtering procedures, a clear improvement of crystal stoichiometry of (Eu,Gd)Te layers was observed as manifested by the increase of Eu2+ intensity in the spectra. Contribution of Eu 4f shell to the total density of states was also analyzed and found at the valence band edge for Eu2+ ions and about 6 eV lower for Eu3+ ions.
5
Content available remote Ferromagnetic transition in Ge1-xMnxTe semiconductor layers
Knoff W., Dziawa P., Osinniy V., Taliashvili B., Domuchowski V., Łusakowska E., Świątek K., Story T.
Materials Science Poland
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2007
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Vol. 25, No. 2
293--300
EN
Magnetic properties of thin layers of p-Ge1-xMnxTe (x < 0.2) semimagnetic (diluted magnetic) semiconductor exhibiting carrier induced ferromagnetism were experimentally studied. The layers were grown on BaF2 (111) substrates by molecular beam epitaxy technique. X-ray diffraction analysis performed at room temperature revealed monocrystalline (111)-oriented rhombohedral (exhibiting ferroelectric properties) crystal structure of Ge1-xMnxTe layers in the entire range of Mn content studied. The examination of the magnetic properties of the layers carried out by superconducting SQUID magnetometry and ferromagnetic resonance technique showed the ferromagnetic transition with the Curie temperature in the range 10-100 K depending on the Mn content and the hole concentration. Contrary to polycrystalline GeMnTe layers, it was experimentally found that in monocrystalline layers of GeMnTe an easy magnetization axis is directed along a normal to the layer plane. This effect is discussed in terms of strain present in these layers due to thermal expansion coefficients mismatch between the substrate and the GeMnTe layer.
6
Content available remote Photoluminescence in EuS-PbS-EuS semiconductor structures with double ferromagnetic barrier
Kowalczyk L., Chernyshova M., Story T., Sipatov A.Yu.
Materials Science Poland
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2006
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Vol. 24, No. 3
809--814
EN
Temperature, magnetic field and laser excitation power dependence of the photoluminescence (PL) was studied in 5x[EuS(5.5 nm)-PbS(17.5 nm)] semiconductor ferromagnetic multilayer grown epitaxially by high vacuum deposition on BaF2 (111) substrate. In EuS-PbS heterostructures ferromagnetic layers of EuS form electron barriers for both electrons and holes in nonmagnetic quantum wells of PbS. The PL was observed in the near infrared due to electronic transitions in PbS quantum wells with narrow energy gap. The measurements carried out at T=4.2 and 77 K (i.e. below and above the Curie temperature of EuS layers equal about 14 K) showed the characteristic PL spectra consisting of one or two lines with strongly nonlinear response upon increasing the YAG laser excitation power. Below the Curie temperature, the application of a weak magnetic field of 200 Oe results in a change of the PL intensity as well as a small red shift of about 1 meV of the PL energy. These observations are discussed in terms of a model taking into account the magnetization dependent height of EuS potential barrier for electrons in PbS quantum well.
7
Content available remote Magnetic properties of (Eu,Gd)Te semiconductor layers
Dziawa P., Osinniy V., Dobrowolski W., Dybko K., Łusakowska E., Taliashvili B., Story T., Smits C.J.P., Swagten H.J.M.
Materials Science Poland
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2006
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Vol. 24, No. 3
777--781
EN
In (Eu,Gd)Te semiconductor alloys a well known antiferromagnetic semiconductor compound EuTe is transformed into n-type ferromagnetic alloy. This effect is driven by the RKKY interaction via conducting electrons created due to substitution of Gd3+ for Eu2+ ions. It is expected that due to the high degree of electron spin polarization (Eu,Gd)Te can be exploited in new semiconductor spintronic heterostructures as a model injector of spin-polarized carriers. The (Eu,Gd)Te monocrystalline layers with Gd content up to 5 at. % were grown by MBE on BaF2 (111) substrates with either PbTe or EuTe buffer layers. The measurements of magnetic susceptibility and magnetization revealed that the ferromagnetic transition with the Curie temperature TC=11- 15 K is observed in (Eu,Gd)Te layers with n-type metallic conductivity. An analysis of the magnetization of (Eu,Gd)Te was carried out in a broad range of magnetic fields applied along various crystal directions both in- and out-of layer plane. It revealed, in particular, that a rapid low field ferromagnetic response of (Eu,Gd)Te layer is followed by a paramagnetic-like further increase towards the full saturatio
8
Content available remote Kronika
Nowina-Konopka M., Story T., Jacyna-Onyszkiewicz Z.
Postępy Fizyki
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2003
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T. 54, z. 2
87-91
PL
Tytuły profesorskie. Stypendia FNP dla młodych naukowców. Jubileusz Andrzeja Budzanowskiego. Nowy dyrektor ICTP. Kosmetyczne nagrody. Rocznice. Program MILAB 2002 w IF PAN. Jak to jest w Holandii. Sezam w Jordanii. Chiny zainteresowane syntezą termojądrową. Osheroff bada katastrofę Columbii. Podwójna helisa za 2 funty. Fundacja BRE-Banku. Henryk Cofta (1922-2003).
9
Content available remote Kronika
Spichał G., Jartych E., Borkowski M., Story T., Szcześniak E.
Postępy Fizyki
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2002
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T. 53, z. 1
51-55
PL
PTF: Oddział Zielonogórski - nowy Oddział PTF. Nagrody FNP 2001. Doktorat h.c. Adama Sobiczewskiego. Będzie wielka nagroda dla matematyków. Sięgnąć dalej. Program MILAB w Instytucie Fizyki PAN. Rzecznik ds. nauki w Holandii. Edward Raymond Andrew (1921 - 2001).
10
Content available remote Międzynarodowa Konferencja Fizyki Półprzewodników, Osaka 2000 [Ze zjazdów i konferencji]
Story T., Dobaczewski L.
Postępy Fizyki
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2001
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T. 52, z. 3
156-157
PL
W dniach 17-22 września 2000 r. w Osace odbyła się 25. Międzynarodowa Konferencja Fizyki Półprzewodników. Komitetowi Organizacyjnemu przewodniczył prof. Hiroshi Kamimura, a pracami Komitetu Programowego kierował prof. Tsuneya Ando. W konferencji wzięło udział 1054 fizyków z 38 krajów świata. Najliczniejszą grupę stanowili gospodarze. Ze zgłoszonych blisko 1300 prac Komitet Programowy zaakceptował (po zasięgnięciu opinii recenzentów) 997 prac (w tym 43 referaty na zaproszenie). 17-osobowa delegacja polska była 10. pod względem liczebności. Przedstawiliśmy 1 referat na zaproszenie (prof. Roman Stępniewski z Uniwersytetu Warszawskiego), a także ok. 20 krótkich referatów i plakatów.
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