Browsing by Author "Gospodinov, M."

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center dot-ray induced effects in Sm-doped strontium borate glasses
(2013)
Marinova, V.
;
Tomov, V.
;
Chuang, C. I.
;
Lin, Y. C.
;
Lin, S. H.
Strontium borate glasses SrB4O7 doped with Sm ions are prepared by conventional melting-quenching method. The effect of center dot-ray irradiation on the glass samples is studied by measuring the absorption spectra and the photoluminescence. It is found that the center dot -ray irradiation caused partial reduction of Sm3+ to Sm2+ at room temperature. Borate framework is supposed to be responsible for the Sm3+ to Sm2+ transition.
Marked enhancement of Neel temperature in strained YMnO(3) thin films probed by femtosecond spectroscopy
(2011-04-01)
Wu, K. H.
;
Chen, H-J
;
Chen, Y. T.
;
Hsieh, C. C.
;
Luo, C. W.
In this paper, the (001)-oriented hexagonal YMnO(3) (h-YMO) thin films with various nominal strain states were deposited on MgO(100), MgO(111) and YSZ(111) substrates by pulsed laser deposition. The ultrafast dynamics probed by wavelength-tunable femtosecond pump-probe spectroscopy was performed to disclose the effects of the epitaxial strain on the electronic structure and associated magnetism. Analyses based on the measured transient-reflectivity-change (Delta R/R) curves revealed that while the magnitude of the on-site Mn d-d transition energy E(dd)(T) changes only slightly with the variation of the lattice constant ratio c/a, a marked shift in the antiferromagnetic (AFM) Neel temperature T(N) was observed and the direction of shift was dependent on the type of strain. The possible mechanism for the observed strain effect on the AFM ordering is discussed. Copyright (C) EPLA, 2011
Marked enhancement of Neel temperature in strained YMnO3 thin films probed by femtosecond spectroscopy
(2011-04-01)
Wu, K. H.
;
Chen, H-J
;
Chen, Y. T.
;
Hsieh, C. C.
;
Luo, C. W.
In this paper, the (001)-oriented hexagonal YMnO3 (h-YMO) thin films with various nominal strain states were deposited on MgO(100), MgO(111) and YSZ(111) substrates by pulsed laser deposition. The ultrafast dynamics probed by wavelength-tunable femtosecond pump-probe spectroscopy was performed to disclose the effects of the epitaxial strain on the electronic structure and associated magnetism. Analyses based on the measured transient-reflectivity-change (Delta R/R) curves revealed that while the magnitude of the on-site Mn d-d transition energy E-dd(T) changes only slightly with the variation of the lattice constant ratio c/a, a marked shift in the antiferromagnetic (AFM) Neel temperature T-N was observed and the direction of shift was dependent on the type of strain. The possible mechanism for the observed strain effect on the AFM ordering is discussed. Copyright (C) EPLA, 2011
Nanomechanical, structural, and transport properties of Bi3Se2Te thin films
(2016-09-15)
Phuoc Huu Le
;
Chiu, Shao-Pin
;
Jian, Sheng-Rui
;
Luo, Chih Wei
;
Lin, Jiunn-Yuan
New ternary phase of Bi3Se2Te thin films were successfully grown through pulsed laser deposition with a single Bi2Se2Te crystal as the target. Bi-rich and Se-and Te-deficient compositions deposited at a substrate temperature (T-s) of 250 degrees C and helium gas pressures (P-He) ranging from 2.0 x 10(-5) to 6.5 x 10(-1) Torr aided the formation of the dominant Bi-rich phase: Bi3Se2Te. The films were grown epitaxially on Al2O3 (001) substrates with Bi3Se2Te [001]//Al2O3 [001] and Bi3Se2Te [110]//Al2O3 [210]. An increase in P-He remarkably enhanced the hardness and Young\'s modulus of the films, primarily because of the decrease in nanograin size, following the HallePetch relationship. Moreover, the Bi3Se2Te films present linear magnetoresistance under a high perpendicular magnetic field (B >= 4 T) and twodimensional weak antilocalization effect under a low B (+/- 1 T) which may be attributed to topological insulator surface state (TSS). Clearly, further theoretical calculations and experiments are needed to confirm the suggested interpretation. (C) 2016 Elsevier B.V. All rights reserved.