Results 1 - 10 of 11
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[en] FePt(50 nm) and [FePt(2,3,5 nm)/AlN(1 nm)]n films were prepared by RF magnetron sputtering technique, then annealed at 550 deg. C for 30 min. This work investigates the effect of the number of bilayer repetitions (n) and AlN concentration on structures and magnetic properties of various [FePt/AlN]n multilayers. The highest coercivities of [FePt/AlN]n multilayers were obtained when n was given as 8. The grain sizes of [FePt/AlN]n films were increased with increasing n. Introducing the non-magnetic AlN not only hindered the growth of FePt particles, but also reduced the intergrain exchange interactions of the [FePt/AlN]n films. And the intergrain interactions were decreased with increasing AlN concentration
[en] FePt and FePt/C thin films were prepared by RF magnetron sputtering, then post-annealed in vacuum. The as-deposited films were in disordered state, and the ordered L10 structure was obtained by post-annealing at 550 deg. C for 30 min. Superlattice peaks (0 0 1) and (1 1 0) can be found in the X-ray diffraction pattern of FePt and FePt/C films, which indicate that the FCC phase has been partially transformed into L10 phase. As the thickness of C layer increased from 1 to 3 nm, the coercivities of the FePt/C multilayer decreased from 6.3 to 1.8 kOe, which indicated that thicker carbon layers in the sample would produce a higher activation energy barrier for the disorder-order transformation. With increasing the C concentration, the grain size and intergrain interactions of FePt/C multilayer films were decreased
[en] A kind of surface-relieved gratings ZrO2 film with high laser damage thresholds is prepared. The ZrO2 sol is achieved by hydro-thermal method, the thin ZrO2 film with the thickness of 1-2 μm, the refractive index of 1.57-1.70, the roughness of 2.3 nm and the laser damage thresholds of 25-30 J/cm2 (1 ns, 1.06 μm) is coated on plastic foil substrate by the speed of 20 m/min at 80-100 degree C. The master structure of the gratings is produced by the holographic optical process of two coherent beams from an argon ion laser source interference. The period of gratings is 1-2 μm and the depth is 70-100 nm. The patterns on the photoresist are transferred to nickel replicas by electroplating process. Finally, the surface-relieved gratings are embossed onto the ZrO2 coated plastic foils using the nickel replicas as stamps. The influences of the period and the depth of the grating, the incident angle and the refractive index of nano-coating to diffraction efficiency are researched. Therefore, this structure provides a feasible approach to detect high-power laser
[en] FePt (50 nm) and [FePt (x nm)/ZrO2 (0.5, 1, 2, 3 nm)]10 (x = 2, 5 nm) films were prepared by RF magnetron sputtering technique, then were annealed at 550 deg. C for 30 min. This work investigates the effect of ZrO2 layer thickness on structures and magnetic properties of FePt/ZrO2 multilayers. The X-ray diffraction results show that superlattice (0 0 1) peaks can be found in FePt (50 nm) and [FePt (5 nm)/ZrO2 (0.5, 1, 2, 3 nm)]10 films. Compared with single layer FePt film, superlattice (0 0 1) peaks of FePt/ZrO2 multilayers are wider and weaker, which indicates that introducing ZrO2 is advantageous to hinder the growth of FePt grains. The coercivities, grain size and intergrain interactions of FePt/ZrO2 films are decreased when ZrO2 layer thickness is increased. And grain volume (V grain) is almost identical to activation volume (V *) for added-ZrO2 films. Thus, the FePt/ZrO2 films with the appropriate coercivities, the small size of grains, and the weak intergrain interactions are obtained
[en] [Co(0.6 nm)/ZnO(x nm)]60 (x= 0.4nm, 3nm) films were deposited on glass substrates then annealed in a vacuum. The magnetisation of the films increased with annealing but not the magnitude of the magneto-optical signals. The dielectric functions Im εxy for the films were calculated using the MCD spectra. A Maxwell Garnett theory of a metallic Co/ZnO mixture is presented. The extent to which this explains the MCD spectra taken on the films is discussed.
[en] A series of Zn1-xCoxO thin films with the atomic fraction, x, in the range of 0.03-0.10 were deposited on glass substrates at room temperature by magnetron co-sputtering technique and subsequently coupled with the post-annealing treatment for half hour at different temperatures (350 deg. C and 500 deg. C) under vacuum. A systematic study was done on the structural, optical and magnetic properties of Zn1-xCoxO thin films as a function of Co concentration and annealing temperature. X-ray diffraction and UV-vis spectroscopy results indicated that there are not any secondary phases and Co2+ substituted for Zn2+ of ZnO host. Magnetic hysteresis loops were observed at room temperature, indicating that both the as-deposited samples and the annealed ones exhibit the room temperature ferromagnetism. It was also found that the magnetic saturation moment per Co atom decreases with increasing Co concentration, while the post-annealing treatment can enhance the magnetic moment of the films effectively
[en] In this paper we study the nonlinear behavior of an electromagnetically induced transparency (EIT) resonance subject to a coherent driving field. The EIT is associated with a Λ three-level system where two hyperfine levels within an electronic ground state are coupled to a common excited state level by a coupling field and a probe field. In addition there is an radio-frequency (rf) field driving a hyperfine transition within the ground state. The paper contrasts two different situations. In one case the rf-driven transition shares a common level with the probed transition and in the second case it shares a common level with the coupled transition. In both cases the EIT resonance is split into a doublet and the characteristics of the EIT doublet are determined by the strength and frequency of the rf-driving field. The doublet splitting originates from the rf-field induced dynamic Stark effect and has close analogy with the Autler-Townes effect observed in three-level pump-probe spectroscopy study. The situation changes when the rf field is strong and the two cases are very different. One is analogous to two Λ three-level systems with EIT resonance associated with each. The other corresponds to a doubly driven three-level system with rf-field-induced electromagnetically induced absorption resonance. The two situations are modeled using numerical solutions of the relevant equation of motion of density matrix. In addition a physical account of their behaviors is given in terms of a dressed state picture
[en] Metallic nanoscale voids can support both localized and propagating plasmons and form plasmonic crystals. However, constructing 1D arrays is crucial for producing plasmonic circuits. In this paper we report the first experimental evidence of plasmons in templated linear arrays of self-assembled structures. Single and multilayer arrays of gold voids have been fabricated by self-assembly of sub-micron polystyrene spheres in V-shaped trenches in silicon, followed by selective area electrodeposition. Angle-dependent dispersion characteristics reveal the existence of localized plasmons.
[en] Coherent transient occurs when a two-level transition is subjected to pulsed laser excitation. The relaxation process of coherent transient depends on both the longitudinal and transverse relaxation parameters of the two-level transition, which is related to the population and coherence decay rates. In this paper we study relaxation process of a new type coherent transients observed by applying a pulsed laser excitation to a two-level transition in the presence of a second strong continuous-wave (cw) coherent field coupling one of the two levels to a third level, that is, in a three-level double-resonance configuration. The relaxation process of coherent transients is studied as a function of relaxation parameters of both the two-level transition excited by the pulsed laser field and the transition coupled by the cw laser field. It is shown that by involving a third level with coherent field the relaxation process of coherent transients of a two-level transition can be modified. Our study illustrates a new way of controlling relaxation process of coherent transients in a two-level transition by a second coherent laser and this has important implication for quantum information storage and quantum computing
[en] We report the results of a sequence of magnetisation and magneto-optical studies on laser ablated thin films of ZnCoAlO and ZnCoO that contain a small amount of metallic cobalt. The results are compared to those expected when all the magnetization is due to isolated metallic clusters of cobalt and with an oxide sample that is almost free from metallic inclusions. Using a variety of direct magnetic measurements and also magnetic circular dichroism we find that there is ferromagnetism within both the oxide and the metallic inclusions, and furthermore that these magnetic components are exchange-coupled when aluminium is included. This enhances both the coercive field and the remanence. Hence the presence of a controlled quantity of metallic nanoparticles in ZnAlO can improve the magnetic response of the oxide, thus giving great advantages for applications in spintronics. (paper)