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1
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Changes in Luminescence of Ce:yag Crystals Under Ionizing Radiation Treatment

100%
Kaczmarek S., Moroz Z., Kwasny M., Kisielewski J., Lukasiewicz T., Wojtkowska J., Rzewuski H.
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vol. 95
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issue 6
953-964
EN
Radiation induced changes in the luminescence spectrum under influence of UV light, γ-rays, electrons and protons for several concentrations of Ce^{3+} ions as well as Mg^{2+} ions in yttrium-aluminum garnet crystals were investigated. To irradiate with γ and electron as grown crystals were used while for proton irradiations the crystals were thermally annealed. For small concentrations of cerium ions (≈0.01 at.%) an increase in the luminescence (about 100%) was observed after gamma irradiation with a dose of 10^{5} Gy. This increase was due to the growth in Ce^{3+} ions concentration after γ-irradiation (≈50%), due to the Ce^{4+} → Ce^{3+} recharging reaction. For highly doped Ce:YAG crystals (0.1 at%, 0.2 at.%) also an increase, but much smaller (4%), for the Mg codoped crystals (0.1 at.%) was observed. After 1 MeV electron irradiation in the over-threshold type interaction a decrease in luminescence is observed due to the domination of the Ce^{3+} → Ce^{4+} ionization process. In the case of the proton irradiation, for small fluencies (≈10^{13} particles/cm^{2}) an increase in luminescence is observed due to the domination of the recharging processes of Ce^{4+} ions. For larger fluencies (>10^{14} particles/cm^{2}) a decrease takes place due to a high level of radiation defects.
2
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Excited State Absorption and Thermoluminescence in Ce and Mg Doped Yttrium Aluminum Garnet

100%
Wiśniewski K., Koepke C., Wojtowicz A., Drozdowski W., Grinberg M., Kaczmarek S., Kisielewski J.
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vol. 95
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issue 3
403-412
EN
In this paper we report preliminary results of optical studies on Y_{3}Al_{5}O_{12} (YAG) crystals codoped with Ce and Mg. By using measurements of luminescence, absorption, and luminescence excitation spectra we demonstrate that although the basic features introduced to the YAG host by the Ce-doping remain intact, the Mg-codoping imposes some significant changes on other properties of the material. These changes are potentially important for laser and/or scintillator applications of YAG:Ce and are due, most likely, to modifications of defect populations in the material. We characterize them by using the techniques of thermoluminescence and excited state absorption under excimer laser pumping. These techniques, interestingly, yield results that seem inconsistent. While the thermoluminescence signal of the Mg-doped sample is strongly reduced, suggesting that trap concentrations in the presence of Mg are suppressed, the excited state absorption signal, which we also relate to the traps, is higher. We offer a tentative explanation of this contradiction between the two experiments that involves a massive transfer of electrons from the Mg-related defects to the excited state absorption centers caused by the excimer pump itself.
3
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UV and Gamma Irradiation Effect in Spectroscopic and Lasing Properties of Er^{3+} doped Yttrium-Aluminium Garnet, Yttrium Orthoaluminate and Lithium Niobate Crystals

84%
Kaczmarek S., Pracka I., Mierczyk Z., Kopczyński K., Piramidowicz R., Malinowski M., Kisielewski J., Matkovskii A., Sugak D.
Acta Physica Polonica A
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1996
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vol. 90
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issue 2
411-418
EN
Optical features (absorption and luminescence spectra) for Er^{3+} doped yttrium-aluminium garnet (YAG), yttrium orthoaluminate (YAP) and LiNbO3 crystals as well as their changes after UV and gamma irradiations are presented. Possibility of gamma-induced sensibilization process in Er^{3+} doped crystals is discussed. Positive result for non-pre-annealed gamma-irradiated rods of Er^{3+}:YAG crystal was stated.
4
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The Influence of He^+ Ion Bombardment on Magnetic Properties of NiFe/Au/Co/Au Multilayers

84%
Kuświk P., Szymański B., Urbaniak M., Stobiecki F., Sveklo I., Kisielewski J., Maziewski A., Jagielski J.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
352-354
EN
The influence of He^+ ion bombardment on magnetoresistance, magnetization reversal and domain structure of sputtered (Ni_{80}Fe_{20}(2 nm)/Au(2 nm)/Co(0.6 nm)/Au(2 nm))_{10} multilayers was investigated. The samples were bombarded using He^+(30 keV) ions with fluences D varied from 10^{13} to 3×10^{16} He^+/cm^{2}. With increasing D the following changes in magnetic properties were observed: (i) exponential decay of the saturation field of Co layers, (ii) progressive decrease in magnetoresistance as a result of degradation of Co layers perpendicular anisotropy, (iii) linear decrease in stripe domain period with log(D).
5
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He⁺ Ion Bombardment Induced Effects on Magnetic Properties of Ni-Fe/Au/Co/Au Films

84%
Kuświk P., Szymański B., Urbaniak M., Dubowik J., Stobiecki F., Kisielewski J., Tekielak M., Maziewski A., Weis T., Ehresmann A.
Acta Physica Polonica A
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2008
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vol. 113
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issue 2
651-656
EN
The influence of He⁺ (10 keV) ion bombardment on magnetic properties of sputter deposited Ni_{80}Fe_{20}/Au/Co/Au layered films was studied. The variable parameters were the thickness of the Co layer or Au spacer and the ion dose. The magnetooptical Kerr measurements were performed on samples with wedge shaped Co or Au layers. With increasing dose of helium ions the following changes in magnetic properties were observed: (i) a decrease in the Co thickness range corresponding to the perpendicular anisotropy, (ii) a decrease in the coercive field (H_C), (iii) an increase in the ferromagnetic coupling between ferromagnetic layers.
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