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Black Holes and Photons with Entropic Force
HE Xiao-Gang, , MA Bo-Qiang,
Chin. Phys. Lett. 2010, 27 (7):
070402
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DOI: 10.1088/0256-307X/27/7/070402
We study the entropic force effects on black holes and photons. It is found that application of an entropic analysis restricts the radial change ΔR of a black hole of radius RH, due to a test particle of a Schwarzschild radius Rh moving towards the black hole by Δx near a black body surface, to be given by a relation RHΔR= RhΔx/2, or ΔR/λM =Δx/2λm. We suggest a new rule regarding entropy changes in different dimensions, ΔS= 2πkDΔl /λ, which unifies Verlinde's conjecture and the black hole entropy formula. We also propose the extension of the entropic force idea to massless particles such as photons. It is realized that there is an entropic force on a photon of energy Eγ, with F = G M (Eγ/c2)/R2, and therefore the photon has an effective gravitational mass mγ= Eγ/c2.
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Optimization and Finite Element Analysis of the Temperature Field in a Nitride MOCVD Reactor by Induction Heating
LI Zhi-Ming, HAO Yue, ZHANG Jin-Cheng, CHEN Chi, CHANG Yong-Ming, XU Sheng-Rui, BI Zhi-Wei
Chin. Phys. Lett. 2010, 27 (7):
070701
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DOI: 10.1088/0256-307X/27/7/070701
A susceptor structure with a ring channel for a vertical metalorganic chemical vapor deposition reactor by induction heating is proposed. Thus the directions of heat conduction are changed by the channel, and the channel makes the heat in the susceptor redistribute. The pattern of heat transfer in this susceptor is also analyzed. In addition, the location and size of the channel in the susceptor are optimized using the finite element method. A comparison between the optimized and the conventional susceptor shows that the optimized susceptor not only enhances the heating efficiency but also the uniformity of temperature distribution in the wafer, which contributes to improving the quality of the film growth.
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Investigation of the Imaging Polarization Effect Based on a Pixellated CdZnTe Detector
LI Miao, XIAO Sha-Li, ZHANG Liu-Qiang, CAO Yu-Lin, CHEN Yu-Xiao, SHEN Min, WANG Xi
Chin. Phys. Lett. 2010, 27 (7):
070702
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DOI: 10.1088/0256-307X/27/7/070702
A pixel array CdZnTe imaging system, employing a 40×40×5 mm3 pixellated CdZnTe detector, is established. The imaging polarization effect in the CdZnTe pixellated detector for a collimated Cs137 Gamma source is investigated in detail. The experimental results for different irradiated fluxes indicate that excessive irradiated flux indeed causes central pixels to be shut off completely. The imaging performance of the polarized detector is severely degraded. Polarized detector counts are simultaneously reduced to one-third of the non-polarized detector counts. A theoretical model of potential distribution is also proposed by solving the Poisson equation and, in turn, the electric potential distortion for high irradiated flux is discussed by comparison with the experimental results.
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Proposed Chiral Doublet Bands in 98Tc
DING Huai-Bo, ZHU Sheng-Jiang, WANG Jian-Guo, GU Long, XU Qiang, XIAO Zhi-Gang, YEOHA Eing-Yee, ZHANG Ming, ZHU Li-Hua, WU Xiao-Guang, LIU Ying, HE Chuang-Ye, WANG Lie-Lin, PAN Bo, LI Guang-Sheng
Chin. Phys. Lett. 2010, 27 (7):
072501
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DOI: 10.1088/0256-307X/27/7/072501
High spin states in odd-odd 98Tc nuclei are studied by in-beam γ-ray spectroscopy with the 96Zr(6Li, 4n) fusion-evaporation reaction at a beam energy of 35 MeV. The previous level scheme is updated. A band based on 1090.7 keV is expanded, and another band based on 1920.6 keV is newly identified. The observed two negative parity bands in 98Tc are proposed to be a pair of chiral doublet bands with the configuration πg9/2 νh11/2. The evidence supporting the assignment of the chiral doublet bands is discussed. Signature splitting and signature inversion are observed in the πg9/2ν h11/2 band in 98Tc.
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Effect of S Substitution for P Point Defects in KDP Crystals: First-Principles Study
GAO Hui, SUN Xun, LIU Bao-An, XU Ming-Xia, HU Guo-Hang, XU Xin-Guang, ZHAO Xian
Chin. Phys. Lett. 2010, 27 (7):
073101
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DOI: 10.1088/0256-307X/27/7/073101
The electronic structure and geometric distribution of phosphor replaced by sulfur in potassium dihydrogen phosphate (KDP) are investigated by first-principles calculations. The point defect narrows down the energy gap to about 4.9 eV, corresponding to a two-photon absorption of 355 nm after correction. This can explain the decrease of the laser damage resistance in KDP crystals. Moreover, the defects twist the crystal structure and weaken bonds, especially the O-H bonds, so these bonds may be the first sites to crack under laser irradiation.
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Theoretical Study of the Influence of Femtosecond Laser Wavelength on the Evolution of a Double-Minimum Electronic Excited State Wave Packet for NaRb
MA Ning, WANG Mei-Shan, XIONG De-Lin, YANG Chuan-Lu, MA Xiao-Guang, WANG De-Hua
Chin. Phys. Lett. 2010, 27 (7):
073301
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DOI: 10.1088/0256-307X/27/7/073301
Employing the two-state model and the time-dependent wave packet method, the influence of femtosecond laser wavelength on the evolution of the double-minimum electronic excited state wave packet is numerically investigated. For different laser wavelengths, evolutions of the double-minimum electronic excited state wave packet with time and internuclear distance are different. One can control the evolution of the wave packet by varying the laser wavelength appropriately, which will benefit the light manipulation of atomic and molecular processes. Furthermore, study of the dynamics of the NaRb molecule may yield clues to creating an ultracold molecule.
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Two Electron Transfer and Stabilization in Slow O6+ and Rare-Gas Collisions
XUE Ying-Li, YU De-Yang, LU Rong-Chun, SHAO Cao-Jie, RUAN Fang-Fang, YANG Zhi-Hu, CAI Xiao-Hong
Chin. Phys. Lett. 2010, 27 (7):
073402
.
DOI: 10.1088/0256-307X/27/7/073402
The stabilization ratios R for double-electron transfer, i.e., the cross section ratios of true double capture to total double-electron transfer, are measured in O6++He, Ne and Ar collisions at 6 keV/u. A high R value about 68% is obtained for the He target, while for the Ar target, the R value is only 8%. The high R value for the He target is due to the significant direct population of the (2l, nl') configurations with high n. For the Ar target, the (quasi)symmetric configurations (3l, nl') lead to the much lower R value. Neglecting the core effects, the O6+ ion can be taken as a bare ion C6+ except the occupied 1s shell, and then the measured R values are compared with previous experimental results of C6+ projectile ions at similar impact velocity. It yields good agreement with the Ne and Ar target, while the occupied 1s shell for the O6++He system results in a higher R value than that in C6++He collisions.
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Stable Narrow Linewidth 689nm Diode Laser for the Second Stage Cooling and Trapping of Strontium Atoms
LI Ye, LIN Yi-Ge, ZHAO Yang, WANG Qiang, WANG Shao-Kai, YANG Tao, CAO Jian-Ping, LI Tian-Chu, FANG Zhan-Jun, ZANG Er-Jun
Chin. Phys. Lett. 2010, 27 (7):
074208
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DOI: 10.1088/0256-307X/27/7/074208
We report stable narrow linewidth laser systems based on self-developed Littman configuration external cavity diode lasers (ECDLs). The frequency of the ECDL is stabilized to a high fineness ultralow-expansion glass reference cavity with the Pound-Drever-Hall technique. By heterodyne beating of two identical systems, we conclude that the linewidth of each ECDL is reduced to lower than 150 Hz and its frequency stability reaches 4.3× 10-14 at an averaging time of 1 s, the averaged long-term frequency drift is less than 0.2 Hz/s over 30 h measurement time.
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Supercontinuum Generation with High Birefringence SF6 Soft Glass Photonic Crystal Fibers
FU Bo, LI Shu-Guang, YAO Yan-Yan, ZHANG Lei, ZHANG Mei-Yan
Chin. Phys. Lett. 2010, 27 (7):
074209
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DOI: 10.1088/0256-307X/27/7/074209
A kind of high birefringence SF6 soft glass photonic crystal fiber (HBSF6-PCF) is proposed. The properties of birefringence, dispersion, nonlinear coefficient and the transmission characteristics are studied by the multipole method and the adaptive split-step Fourier method. The numerical results show that the birefringence and the nonlinear coefficient reach the orders of 10-2 and 10-1, respectively. In addition, the HBSF6-PCFs can generate very smooth supercontinuum spectra when illuminated with femtosecond pulsed light of 1064 nm. It is found that up to 800 nm spectral width (evaluated at -5 dB from the peak) is achieved. Therefore, the advantage of the HBSF6-PCFs is such that a high birefringence, a high nonlinearity and a smooth supercontinuum are perfectly combined in them.
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Narrow Linewidth Tm3+-Doped Large Core Fiber Laser Based on a Femtosecond Written Fiber Bragg Grating
ZHANG Yun-Jun, WANG Wei, ZHOU Ren-Lai, SONG Shi-Fei, TIAN Yi, WANG Yue-Zhu
Chin. Phys. Lett. 2010, 27 (7):
074214
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DOI: 10.1088/0256-307X/27/7/074214
A diode laser (LD) clad-pumped narrow linewidth all-fiber Tm3+-doped fiber laser is reported with a maximal output power of 27 W at 1.947μm. By successively splicing an LD pigtail fiber, a single-mode Tm3+-doped fiber, and a multi-mode Tm3+-doped fiber, the fiber laser has 70 pm narrow linewidth output, and a high slope efficiency of nearly 47.5% with respect to the launched pump power. The high reflectivity fiber Bragg gratings, which are directly written into the single-mode Tm3+-doped fiber core by the 800 nm femtosecond pulsed laser, act as the high reflectivity coupler. The output laser has diffraction-limited beam quality with a factor M2 of 1.29, when the output laser power is nearly 27 W.
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Laser Resistance of Ta2O5/SiO2 and ZrO2/SiO2 Optical Coatings under 2μm Femtosecond Pulsed Irradiation
LIU Na, WANG Ying-Jian, ZHOU Ming, JING Xu-Feng, WANG Yan-Zhi, CUI Yun, JIN Yun-Xia
Chin. Phys. Lett. 2010, 27 (7):
074215
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DOI: 10.1088/0256-307X/27/7/074215
Ta2O5/SiO2 and ZrO2/SiO2 high reflecting (HR) coatings are prepared by ion beam sputtering and electron beam evaporation, respectively. The laser-induced damage thresholds (LIDTs) of these samples are investigated with 2 μm femtosecond pulse lasers (80 fs, 1 kHz). It is found that the Ta2O5/SiO2 HR coating has a higher capability of laser damage resistance than the ZrO2/SiO2 HR coating in the 2 μm femtosecond regime. The scanning electron microscope results show that the damage sites of the ZrO2/SiO2 HR coating have a relatively porous structure, the loose structure of coatings will provide more sites for water molecules, and the LIDTs of HR coatings will be reduced as a result of the strong water absorption at the wavelength of 2 μm.
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Performance of Non-Contact Linear Actuators Driven by Surface Acoustic Waves*
CHENG Li-Ping, ZHANG Shu-Yi, GU Huan-Huan, ZHOU Feng-Mei, SHUI Xiu-Ji
Chin. Phys. Lett. 2010, 27 (7):
074302
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DOI: 10.1088/0256-307X/27/7/074302
A new kind of non-contact linear actuator (motor) driven by surface acoustic waves (SAWs) is presented, in which the stators are made from SAW delay lines using 128° YX-LiNbO3 substrates. A fluid layer is introduced between the slider and the stator of the actuator, and the slider is a circular aluminum disk suspended on the surface of the liquid (water) layer. As the SAW is excited on the stator, the SAW is converted to a leaky wave in the interface of the stator and the liquid, and then propagates into the liquid. Owing to the nonlinear effect of wave propagation, acoustic streaming is generated, which pushes the slider to move. By the experiments, the relations between the slider velocity and the experimental parameters, such as the exciting voltage of the SAWs, the thickness and the kinematic viscosity of the liquid layer, are obtained.
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Symmetric and Anti-Symmetric Lamb Waves in a Two-Dimensional Phononic Crystal Plate
LI Yong, HOU Zhi-Lin, FU Xiu-Jun, Badreddine M Assouar
Chin. Phys. Lett. 2010, 27 (7):
074303
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DOI: 10.1088/0256-307X/27/7/074303
It is well known that Lamb waves in a plate with a mirror plane can be separated into two uncoupled sets: symmetric and anti-symmetric modes. Based on this property, we present a revised plane wave expansion method (PWE) to calculate the band structure of a phononic crystal (PC) plate with a mirror plane. The developed PWE method can be used to calculate the band structure of symmetric and anti-symmetric modes separately, by which the depending relationship between the partial acoustic band gap (PABG), which belongs to the symmetric and anti-symmetric modes alternatively, and the position of the scatterers can be determined. As an example of its application, the band structure of the Lamb modes in a two-dimensional PC plate with two layers of void circular inclusions is investigated. The results show that the band structure for the symmetric and anti-symmetric modes can be changed by the position of the scatterers drastically, and larger PABGs will be opened when the scatterers are inserted into the area of the plate, where the elastic potential energy is concentrated.
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Non-Uniformity of Ion Implantation in Direct-Current Plasma Immersion Ion Implantation
LIU Cheng-Sen, WANG De-Zhen, FAN Yu-Jia, ZHANG Nan, GUAN Li, YAO Yuan
Chin. Phys. Lett. 2010, 27 (7):
075201
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DOI: 10.1088/0256-307X/27/7/075201
A particle-in-cell simulation is developed to study dc plasma immersion ion implantation. Particular attention is paid to the influence of the voltage applied to the target on the ion path, and the ion flux distribution on the target surface. It is found that the potential near the aperture within the plasma region is not the plasma potential, and is impacted by the voltage applied to the implanted target. A curved equipotential contour expands into the plasma region through the aperture and the extent of the expansion depends on the voltage. Ions accelerated by the electric field in the sheath form a beam shape and a flux distribution on the target surface, which are strongly dependent on the applied voltage. The results of the simulations demonstrate the formation mechanism of the grid-shadow effect, which is in agreement with the result observed experimentally.
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Influence of Fe Contamination on the Minority Carrier Lifetime of Multi-crystalline Silicon
MENG Xia-Jie, MA Zhong-Quan, LI Feng, SHEN Cheng, YIN Yan-Ting, ZHAO Lei, LI Yong-Hua, XU Fei
Chin. Phys. Lett. 2010, 27 (7):
076101
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DOI: 10.1088/0256-307X/27/7/076101
We investigate the influence of Fe contamination on the minority carrier lifetimes of multi-crystalline silicon. The minority carrier lifetime is measured by the microwave photoconductive decay method. The original bulk lifetime is about 30 μs after passivation with iodine solution. After intentional Fe contamination, the bulk lifetime declines with increasing temperature. Fast cooling in air conduces to the formation of more interstitial Fe ([Fe]i). Slow cooling through the control of the furnace temperature limits the formation of more [Fe]i, but leads to the formation of precipitation. The data support the idea that the minority carrier lifetime in multi-crystalline silicon mainly depends on the distribution of Fe but not the total amount. A favorite effect of [Fe]i gettering is discovered after conventional phosphorus diffusion, and the [Fe]i concentration remaining in the silicon wafer is acceptable for solar cell applications.
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Evolutions of Crystal Structure, Stoichiometry and Electrochemical Behavior with Co Substitution in LiNi1-yCoyO2 Positive Electrodes
XIA Rong-Sen, CUI Zhong-Hui, LIU Bi-Qiu, GUO Xiang-Xin, ZHAO Jing-Tai
Chin. Phys. Lett. 2010, 27 (7):
076102
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DOI: 10.1088/0256-307X/27/7/076102
LiNi1-yCoyO2(0.1≤ y≤0.4) positive electrode materials are synthesized by a chemical method with stoichiometric acetates of related cations. Their crystal structure, stoichiometry and electrochemical behaviors versus Co concentration are investigated by x-ray diffraction, synchrotron-based x-ray absorption fine structure and galvanostatic cycling measurements. The results reveal that the non-stoichiometric Ni2+, Li/Ni cation mixing and polarization are reduced as the amount of Co substitution increases, clearly indicating that the Co element is a medium for easily oxidizing Ni2+ to Ni3+ during the synthesis process.
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Influence of Rare-Earth Substitution for Iron in FeCrMoCB Bulk Metallic Glasses
Abderrezak Bouchareb, Badis Bendjemil, , Rafael Piccin, Marcello Baricco
Chin. Phys. Lett. 2010, 27 (7):
076103
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DOI: 10.1088/0256-307X/27/7/076103
The effects of rare earth addition on the glass forming ability of Fe50-xCr15Mo14C15B6Mx (x=0, 2 and M=Y, Gd) bulks and ribbons are studied. The thermal and structural properties of the samples are measured by a combination of differential scanning calorimetry (DSC), x-ray diffraction and scanning electron microscopy. Chemical compositions are checked by energy dispersive spectroscopy analysis. The copper mold casting technique leads to a fully amorphous structure up to 2 mm only for compositions containing Y or Gd. In the case of ribbons, a fully amorphous phase is observed for all the compositions. The roles of Y and Gd are discussed on the basis of melting behavior analyzed by high-temperature DSC. Such elements act as oxygen scavengers, avoiding heterogeneous nucleation.
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A Simple Theoretical Method to Predict the Hardness of Pure Metal Crystals
JIN Yun-Fei, YE Xiang-Xi, LI Jing-Tian, ZHANG Wen-Xian, ZHUANG Jun, NING Xi-Jing,
Chin. Phys. Lett. 2010, 27 (7):
076201
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DOI: 10.1088/0256-307X/27/7/076201
Design of superhard bulk materials requires predicting their hardness, challenging current theories for material design. By introducing a concept of condensing force (CF), it is shown via initio calculations for fcc (Ni, Cu, Al, Ir, Rh, Au, Ag, Pd) and hcp Re crystals that materials with larger CF can have greater hardness. Since the calculation of CF is easy, this method might prove a convenient way to evaluate the hardness of newly designed materials.
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Transition to Film Boiling in Microgravity: Influence of Subcooling
ZHAO Jian-Fu, LI Jing, YAN Na, WANG Shuang-Feng
Chin. Phys. Lett. 2010, 27 (7):
076401
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DOI: 10.1088/0256-307X/27/7/076401
The transition process to film pool boiling in microgravity is studied experimentally aboard the Chinese recoverable satellite SJ-8. A quasi-steady heating method is adopted, in which the heating voltage is controlled to increase exponentially with time. Small, primary bubbles are formed and slid on the surface, which coalesce with each other to form a large coalesced bubble. Two ways are observed for the transition from nucleate to film boiling at different subcoolings. At high subcooling, the coalesced bubble with a smooth surface grows slowly. It is then difficult for the coalesced bubble to cover the whole heater surface, resulting in a special region of transition boiling in which nucleate boiling and local dry areas can coexist. In contrast, strong oscillation of the coalesced bubble surface at low subcooling may cause rewetting of local dry areas and activation of more nucleate sites, resulting in an abrupt transition to film boiling.
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Band Structures of Metal-Oxide Capped Graphene: A First Principles Study
LIU Han, SUN Qing-Qing, CHEN Lin, XU Yan, DING Shi-Jin, ZHANG Wei, ZHANG Shi-Li
Chin. Phys. Lett. 2010, 27 (7):
077201
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DOI: 10.1088/0256-307X/27/7/077201
We perform a first-principles calculation based on density functional theory to investigate the interface between single layer graphene and metal oxides. Our study reveals that the monolayer graphene becomes semiconducting by single crystal SiO2 and Al2O3 contact, with energy gaps to ~0.9 and ~1.8 eV, respectively. We find the gap originates from the breakage of π bond integrity, whose extent is related to the interface atom configuration. We believe that our results highlight a promising direction for the feasibility to apply large scale graphene layers as building blocks in future electronics devices.
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Influence of Substrate on the Transportation Properties of Co/Alq3 Granular Films on a Si Wafer
ZHANG Yan, SHENG Peng, LIU Wen-Ming, SHU Qi, GU Zhi-Hua, NI Gang,
Chin. Phys. Lett. 2010, 27 (7):
078102
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DOI: 10.1088/0256-307X/27/7/078102
A series of Co0.48(Alq3)0.52 granular films were deposited on silicon substrates using the co-evaporating technique. A crossover of magnetoresistance (MR) from negative to positive was observed in the samples, due to conducting channel switching. The transport properties of samples are greatly influenced by hydrofluoric acid pretreatment, as a result, positive MR decreases drastically and the temperature dependence of resistance changes a lot near room temperature. The result indicates that the native oxide layer plays an important role in the transport mechanism. Moreover, different resistivities of Si substrates influence the current distribution of conducting channels, leading to different transport behaviors accordingly.
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Magnetic Properties and Magnetoresistance of CdMnS:Au Based Structures Prepared by Co-evaporation
HE Jun, LI Ming, D. H. Kim, J. C. Lee, D. J. Lee, FU De-Jun, T. W. Kang
Chin. Phys. Lett. 2010, 27 (7):
078501
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DOI: 10.1088/0256-307X/27/7/078501
Polycrystalline CdMnS and CdMnS:Au films with hexagonal structure on Si(111) substrates are prepared by co-evaporation, and exhibit ferroelectric and ferromagnetic properties, respectively. Under optimized growth conditions, CdMnS:Au samples with an average crystallite size of 90 nm and Mn concentration of 5.0 at.% are obtained, and an all-semiconductor spin valve device of Co/Au/CdMnS:Au/CdMnS/Pt is fabricated. Electrical measurement of the device reveals the clear dependence of resistance on applied magnetic field, with a relative magnetoresistance of 0.06% and a switching field of 100 Oe at 77k
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Reply to “Comment on ‘Q-switched Tm:YAG Laser Intracavity-Pumped by a 1064nm Laser’ ”
MA Qing-Lei, ZONG Nan, XIE Shi-Yong, YANG Feng, GUO Ya-Ding, XU Jia-Lin, BO Yong, PENG Qin-Jun, CUI Da-Fu, XU Zu-Yan
Chin. Phys. Lett. 2010, 27 (7):
079902
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DOI: 10.1088/0256-307X/27/7/079902
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84 articles
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