Spin-polarized two-dimensional electron states (2DESs) at surfaces and interfaces of magnetically active materials attract immense interest because of the idea of exploiting fermion spins rather than ...charge in next generation electronics. Applying angle-resolved photoelectron spectroscopy, we show that the silicon surface of GdRh2Si2 bears two distinct 2DESs, one being a Shockley surface state, and the other a Dirac surface resonance. Both are subject to strong exchange interaction with the ordered 4f-moments lying underneath the Si-Rh-Si trilayer. The spin degeneracy of the Shockley state breaks down below ~90 K, and the splitting of the resulting subbands saturates upon cooling at values as high as ~185 meV. The spin splitting of the Dirac state becomes clearly visible around ~60 K, reaching a maximum of ~70 meV. An abrupt increase of surface magnetization at around the same temperature suggests that the Dirac state contributes significantly to the magnetic properties at the Si surface. We also show the possibility to tune the properties of 2DESs by depositing alkali metal atoms. The unique temperature-dependent ferromagnetic properties of the Si-terminated surface in GdRh2Si2 could be exploited when combined with functional adlayers deposited on top for which novel phenomena related to magnetism can be anticipated.
Spin-polarized two-dimensional electron states (2DESs) at surfaces and interfaces of magnetically active materials attract immense interest because of the idea of exploiting fermion spins rather than ...charge in next generation electronics. Applying angle-resolved photoelectron spectroscopy, we show that the silicon surface of GdRh2Si2 bears two distinct 2DESs, one being a Shockley surface state, and the other a Dirac surface resonance. Both are subject to strong exchange interaction with the ordered 4f-moments lying underneath the Si-Rh-Si trilayer. The spin degeneracy of the Shockley state breaks down below ~90 K, and the splitting of the resulting subbands saturates upon cooling at values as high as ~185 meV. The spin splitting of the Dirac state becomes clearly visible around ~60 K, reaching a maximum of ~70 meV. An abrupt increase of surface magnetization at around the same temperature suggests that the Dirac state contributes significantly to the magnetic properties at the Si surface. We also show the possibility to tune the properties of 2DESs by depositing alkali metal atoms. The unique temperature-dependent ferromagnetic properties of the Si-terminated surface in GdRh2Si2 could be exploited when combined with functional adlayers deposited on top for which novel phenomena related to magnetism can be anticipated.
Nanosecond lasers have recently been widely involved in human activity. However, high-intensity laser radiation can cause severe damage to organs of vision and expensive photonic devices. Radiation ...in the near UV range is especially dangerous for human eyes, since it is strongly absorbed by biological media and is also invisible, i.e., the reaction time of the eye to such radiation is much lower than that of visible light. Passive limiters have high transmission (>70%) at a low light intensity and begin to “darken” only when the threshold value of the laser radiation intensity is reached. In this work, we studied liquid nanodispersed nonlinear optical limiters based on hybrids of single-walled carbon nanotubes (SWCNTs) with metal-free tetra(hydroxy)phthalocyanine (OH)4PcHH). The value of the hydrodynamic radius of separate particles after (OH)4PcHH binding increased from 288 ± 55 nm to 350 ± 60 nm, which confirms the attachment of phthalocyanine complexes to nanotubes. The third harmonic of a Nd:YAG nanosecond laser (355 nm, 20 ns) was used to study the nonlinear optical response. Based on a Z-scan with open-aperture and input-output dependence curves, third-order nonlinear optical absorption coefficients of 149, 236, and 229 cm/GW were obtained for dispersions of composites of SWCNTs and (OH)4PcHH in water, dimethylformamide (DMF), and dimethylsulfoxide (DMSO), respectively. Threshold values did not exceed 100 mJ/cm2. The Z-scan showed a gradual decrease in the duration of the laser pulse by 53%; however, near the focus, there was a sharp increase in the duration of the transmitted pulse, reaching a value of 29 ns in z = 0. This phenomenon confirms the occurrence of reverse saturable absorption in the investigated media and can be used in photonic devices to control the temporal characteristics of the signal. Thus, the possibility of protection of sensitive photonic devices and human eyes from nanosecond laser pulses in the near UV range by nanodispersed liquid media based on composites of SWCNTs with (OH)4PcHH has been discussed in this paper.
In the present research, experiments on the formation and retention of nanoparticles (NPs) in the plasma of radio frequency (RF) capacitive discharge in acetylene were carried out with vertically ...positioned internal electrodes. It has been shown via SEM and TEM techniques that NPs found on the horizontal tube wall after the discharge operation have a spherical shape with a predominant diameter of approximately 400–600 nm. HRTEM analysis reveals their amorphous structure. At the same time, such NPs were not found on vertical electrodes, only a polymer film was deposited. To elucidate the possibility of NPs leaving the plasma in the direction of vertical electrodes, a model of NP retention in the near-electrode sheath of an RF capacitive discharge was elaborated. The model has shown that nanometer- and even micrometer-sized particles formed in the plasma cannot cross the near-electrode sheath and reach the electrode surface. For the plasma consisting of three charged components (positive ions, electrons, and NPs), an analytical model of ambipolar diffusion was developed. Applying this model, it has been shown that the ambipolar electric field can keep the micrometer-sized NPs in the plasma if their concentration is low. However, in the case of a high concentration of NPs, they can be retained with a diameter of no more than a few hundred nanometers due to a significant decrease in the ambipolar electric field. The calculation results are in agreement with our experimental data.
Magnitnoe Obzhatie (MAGO)/magnetized target fusion (MTF) thermonuclear experiments executed with a goal of producing the target plasma heated up to temperatures of hundreds of electronvolts, intended ...for subsequent compression by an imploding liner accelerated by explosion products, are reviewed. In MAGO/MTF experiments, plasma chambers were used consisting of two or three compartments connected by narrow nozzles: acceleration cylinder compartment and deceleration/fusion compartments (cylindrical or hemispherical). A technology of plasma chamber laboratory conditioning is described. Neutron and soft X-ray pulses are presented and obtained in experiments with chambers powered by an explosive magnetic generator. Irrespective of the chamber geometry and number of compartments, the X-ray pulse consists of a highly intensive peak with a duration of 1μs and more than a 10-μs-long low-intensity tail. The neutron pulse is time coincident with the X-ray peak. Yields up to 10 13 neutrons were detected in experiments with two-compartment chambers. Three-compartment chambers with an intermediate compartment are believed to be more promising for the compression. The results are described of the latter MAGO-IX experiment, the only successful experiment with the three-compartment chamber, in which the yield of 2 × 10 12 neutrons was detected in the third compartment and the yield in the middle compartment was many times lower.
New configuration of experiments for MAGO program Burenkov, Oleg M.; Dolin, Yuriy N.; Duday, Pavel V. ...
2012 14th International Conference on Megagauss Magnetic Field Generation and Related Topics (MEGAGAUSS),
2012-Oct.
Conference Proceeding
The paper presents the current status of MAGO research and the basic results of the latest explosive experiments. The program of activities aimed at preparation and conduct of experiments on finish ...compression of high-temperature plasma generated in the thermonuclear compartment of the electric-discharge chamber will be described.
Electromagnetic implosion of the cylindrical condensed liners is of great interest for the studies of high energy density physics, and in particular for getting pressures of terapascal range and for ...measuring the Hugoniots of materials under such pressures. The pulsed power systems on the basis of disk explosive magnetic generators (DEMG) provide the highest currents in the liner loads. A device on the basis of a 15-element DEMG Ø 0.4 m with a foil current opening switch and an explosive closing switch connecting the load is being developed to explore a possibility of driving the aluminum liner to a velocity of ~ 20 km/s and using it as an impactor. It is planned to check the operability of this device in the joint VNIIEF-LANL experiment ALT-3. To test the key systems of the ALT-3 assembly, a series of model experiments has been conducted. The model units will be described, the setup of the experiments testing the operability of the explosive current closing switch able to commute the currents of 60 - 70 MA and the system of high-voltage insulation of the line delivering the energy to the liner and able to withstand high voltages will be discussed. The experiment with the system modeling the ALT-3 device to check the scheme of operation of the pulsed power source' elements and the operability of disk elements under the explosive magnetic regime at the initial feeding current of 7.0 - 7.5 MA will be considered.
