79 resultados para Mn2
Resumo:
Based on a modified mean-field model, we calculate the Curie temperatures of Fe2+- and Co2+-doped diluted magnetic semiconductors (DMSs) and their dependence on the hole concentration. We find that the Curie temperatures increase with an increase in hole concentration and the relationship T(C)proportional to p(1/3) also approximately holds for Fe2+- and Co2+-doped systems with moderate hole concentration. For either low or high hole concentrations, however, the p(1/3) law is violated due to the anomalous magnetization of the Fe2+ and Co2+ ions, and the nonparabolic nature of the hole bands. Further, the values of T-C for Fe2+- and Co2+-doped DMSs are significantly higher than those for Mn2+-doped DMSs, due to the larger exchange interaction strength.
Resumo:
Using a solution-based chemical method, we have prepared ZnS nanocrystals doped with high concentration of Mn2+. The X-ray diffraction analysis confirmed a zinc blende structure. The average size was about 3 nm. Photoluminescence spectrum showed room temperature emission in the visible spectrum, which consisted of the defect-related emission and the T-4(1)-(6)A(1) emission of Mn2+ ions. Compared with the undoped sample, the luminescence of the ZnS:Mn sample is enhanced by more than an order of magnitude, which indicated that the Mn2+ ions can efficiently boost the luminescence of ZnS nanocrystals.
Resumo:
The PL spectra for the 10, 4. 5, 3. 5, 3, 1 nm sized ZnS:Mn2+ nanoparticles and corresponding bulk material under different pressures were investigated. The orange emission band originated from the T-4(1)-(6)A(1) transition of Mn2+ ions showed obvious red shift with the increasing of pressures. The pressure coefficients of Mn-related emissions measured from bulk, 10, 4. 5, 3.5 and 3 nm samples are -29.4 +/- 0.3, -30.1 +/- 0.3, -33.3 +/- 0.6, -34.6 +/- 0.8 and -39 +/- 1 meV/GPa, respectively. The absolute value of the pressure coefficient increases with the decrease of the size of particles. The size dependence of crystal field strength Dq and Racah parameter B accounts for the size behavior of the Mn-related emission in ZnS:Mn nanoparticles. The pressure behavior of Mn-related emission in the 1 nm sized sample is somewhat different from that of other nanoparticles. It may be due to smaller size of 1 nm sample and the special surface condition since ZnS nanoparticles are formed in the cavities of ziolite-Y for the 1 nm sample.
Resumo:
The pressure dependence of the photoluminescence from ZnS : Mn2+, ZnS : Cu2+, and ZnS : Eu2+ nanoparticles were investigated under hydrostatic pressure up to 6 GPa at room temperature. Both the orange emission from the T-4(1) - (6)A(1) transition of Mn2+ ions and the blue emission from the DA pair transition in the ZnS host were observed in the Mn-doped samples. The measured pressure coefficients are -34.3(8) meV/GPa for the Mn-related emission and -3(3) meV/GPa for the DA band, respectively. The emission corresponding to the 4f(6)5d(1) - 4f(7) transition of Eu2+ ions and the emission related to the transition from the conduction band of ZnS to the t(2) level of Cu2+ ions were observed in the Eu- and Cu-doped samples, respectively. The pressure coefficient of the Eu-related emission was found to be 24.1(5) meV/GPa, while that of the Cu-related emission is 63.2(9) meV/GPa. The size dependence of the pressure coefficients for the Mn-related emission was also investigated. The Mn emission shifts to lower energies with increasing pressure and the shift rate (the absolute value of the pressure coefficient) is larger in the ZnS : Mn2+ nanoparticles than in bulk. Moreover, the absolute pressure coefficient increases with the decrease of the particle size. The pressure coefficients calculated based on the crystal field theory are in agreement with the experimental results. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Resumo:
Time-resolved Kerr rotation measurement in the (Ga,Mn)As diluted magnetic semiconductor allows direct observation of the dynamical properties of the spin system of the magnetic ions and the spin-polarized holes. Experimental results show that the magnetic ions can be aligned by the polarized holes, and the time scales of spin alignment and relaxation take place in tens and hundreds of picoseconds, respectively. The Larmor frequency and effective g factor obtained in the Voigt geometry show an unusual temperature dependence in the vicinity of the Curie temperature due to the exchange coupling between the photoexcited holes and magnetic ions. Such a spin coherent precession can be amplified or destructed by two sequential excitation pulses with circularly copolarized or oppositely polarized helicity, respectively. (c) 2006 American Institute of Physics.
Resumo:
Magnetophotoluminescence properties of Zn0.88Mn0.12Se thin films grown by metal-organic chemical vapor deposition on GaAs substrates are investigated in fields up to 10 T. The linewidth of the excitonic luminescence peaks decreases with the increasing magnetic field (< 1 T), but the peak energy is almost unchanged. There is a crossover of the photoluminescence intensities between interband and bound excitonic transitions as the magnetic field is increased to about 1 T. These behaviors are interpreted by the strong tuning of the local alloy disorder potential by the applied magnetic field. In addition, the magnetic field-induced suppression of the energy transfers from excitons to Mn2+ ions is also observed.
Resumo:
Manganese-gallium oxide nanowires were synthesized via in situ Mn doping during nanowire growth using a vapor phase evaporation method. The microstructure and composition of the products were characterized via transmission electron microscopy (TEM), field emission scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. The field and temperature dependence of the magnetization reveal the obvious hysteresis loop and large magnitude of Curie-Weiss temperature. The photoluminescence of the manganese-gallium oxide nanowires were studied in a temperature range between 10 and 300 K. A broad green emission band was observed which is attributed to the T-4(1)-(6)A(1) transition in Mn2+ (3d(5)) ions. (c) 2005 Elsevier B.V. All rights reserved.
Resumo:
The temperature dependences of the orange and blue emissions in 10, 4.5, and 3 nm ZnS:Mn nanoparticles were investigated. The orange emission is from the T-4(1)-(6)A(1) transition of Mn2+ ions and the blue emission is related to the donor-acceptor recombination in the ZnS host. With increasing temperature, the blue emission has a red-shift. On the other hand, the peak energy of the orange emission is only weakly dependent on temperature. The luminescence intensity of the orange emission decreases rapidly from 110 to 300 K for the 10 nm sample but increases obviously for the 3 nm sample, whereas the emission intensity is nearly, independent of temperature for the 4.5 nm sample. A thermally activated carrier-transfer model has been proposed to explain the observed abnormal temperature behaviour of the orange emission in ZnS:Mn nanoparticles.
Resumo:
(magnetic resonance imaging, MRI)MRI30%~40% (1) MRI Gd-DTPA(Gd-DTPA-CMAG-An)Gd-DTPA(Gd-DTPA-CMDn-Cyst)Gd-DTPA-CMAG-AnGd-DTPA-CMAG-AnGd-DTPA1.4Gd-DTPA-CMAG-A2Gd-DTPA2.0Gd-DTPA-CMAG-A2MRIGd-DTPA-CMDn-CystGd-DTPA-CMD4-CystGd-DTPA-CMD4-Cyst (2) MnNaY MRI Mn2+NaYMnNaYMnNaYGd-DTPAMn2+NaY(3.2%~5.2%)MnNaY (3.2% Mn) (3) MRI GL-(A-Gd-DTPA)3Gd-DTPA1.4()GLGAGd-DTPA GL (4) Gd-DTPA Gd-DTPAGd-DTPA-BBAGd-DTPA-BtBAGd-DTPA
Resumo:
Eu2+ab-Zn3(PO4)2:Mn2+-Zn3PO42:Mn2+Zn3B2O6:Mn2+Y2O3Eu3+Ca8MgSiO44Cl2:Eu2+Zn4B6O13:Mn2+-Zn3(PO4)2Mn2+Zn2SiO4:Mn2+Y2O2S:Eu3+caOEu3-Zn3(PO4)2:Mn2+Ga3+Zn2SiO4:Mn2+Al3+
Resumo:
Eu~3Sm~3Mn~2Fe~3Co~2Ni~2ZnOcccc10Onm15357-366nmEu3+Sm3Mn2+Fe3Co2Ni2Zn2+O2- Eu3+ZnO363nm368nmEg=3.423.40evEu3Zn1-xEux0.005x0.15Zn1-xTMxO356nm-369nm3.34-3.46eVCo2d-dZn1-xCoxO60Zn1-xEuxO90Zn1-xEuxO613nmEu37F5D378nmZnO394nmEu3+5D07FJJ1234zno378nmEu3+5D07F2znoE4-400KZn0.9Eu0.1OznogCooIO23oK200KM-HBr021emgHc327OeZn0.9Mn0.1OZn0.9Ni0.1OZn0.9Co0.1O80KZn0.9Eu0.1OZT110K14.53Zn1-xTMxOCoFeNiMnZn1-xTMxO80Co2DMSsol-gelZnoTMMCM-41AAOZnO:TMMCM-41MCM-41AAoloonmMCM-41Zn0.9Co0.1O80K-30OKMnFeNiZnoAAOZnO:TM(TM=MnFeCoNiSOK-30OKZnO:AABuSmcoZnlxCoxOPH5ZnORERE=EuSmZn0.98Co0.02O80KZnOREREEuSm80K
Resumo:
ZnS:Mn.,Mn2+4T1-6A1.10,4.5,3.5,3 nmZnS:MnMn2+-29.40.3-30.10.3,-33.30.6,-34.60.8,-391 meV/GPa,,DqRacahB.1nmMn2+,,Y.
Resumo:
/PncAPncA22.4 KDapH6.6 ~ 7.435 ~ 45 CPncAMn2+Fe2+1:1PncAPncA9PncA9D8K96C138PncAD49H51H57H71Y103S104Pyrococcus horikoshii PncA, , 19pncAPncA78.9 %16
Resumo:
1758-3600m 6175826203200350035873600m22540185225 1.2251028452251010928 1604511745B1394873U/ml16SrDNAB1394Bacillus subtilis60pH 8.0 405060 Mn2+ Mg2+ Ca2+Hg2+ Fe3+ Cu2+ Zn2+ Fe2+PMSF 2.10040 Rhizoctonia solaniCandida albicans373537%35%1845%SHA6Fusarium oxysporum10SHA6, SHA6Aurantimonas altamirensis 3.205SHA4100g/ml83%,400ppm48h38%SHA4Nocardiopsis sp
Resumo:
(CMC):(AA)/=10,()(N,N-)0.00140.0015.,CMC400~45016h,Zn2+Cu2+Pb2+Cd2+Cr2+Ni2+Mn2+.,CMC,pH,pH9;CMCPb2+Cu2+.
