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1.
The effect of an array of ferromagnetic nanoparticles on the field-dependent critical current of the short overlap Josephson junction is experimentally studied. Large reversible variations of the maximum critical current are observed depending on the magnetic state of the particles. The pronounced commensurability effects are detected which are proved by the additional peaks of magnetic field induced diffraction pattern.  相似文献   
2.
The properties of Mn-doped GaAs layers grown by laser deposition were investigated with measurements of Hall effect and magneto-optical Kerr effect (MOKE). The electrical and magnetic parameters of the layers were defined by growth temperature and quantity of sputtered Mn. It was shown that room-temperature ferromagnetism is revealed by MOKE and, after ruby laser 25 ns pulse annealing, by Hall effect measurements.  相似文献   
3.
Komandin  G. A.  Nozdrin  V. S.  Fedorov  P. P.  Osiko  V. V. 《Doklady Physics》2019,64(7):271-275
Doklady Physics - Transmission spectra of a single crystal and artificial and natural ceramics of fluorite have been obtained in the transparency regions of the material in the THz and mid-IR...  相似文献   
4.
Physics of Particles and Nuclei Letters - The construction of an experimental facility with test electron beams is under way at the Dzhelepov Laboratory of Nuclear Problems at the Joint Institute...  相似文献   
5.
The results are reported on the observation of the induced emission from CdxHg1?x Te samples optically pumped by a pulsed Nd:YAG laser at temperatures T<77 K. In the wave range λ~ 3300–3600 nm, both stimulated and spontaneous emission were observed. The experimentally measured emission spectra are analyzed. The properties of the spectra from the samples are discussed and the possible applications are considered.  相似文献   
6.
Using a local technique, we study the microwave radiation power P3(T,P,Hdc) at the triple frequency of the main signal as a function of the temperature T, the input power P, and the external magnetic field Hdc perpendicular to the superconductor surface for YBa2Cu3O7 (YBCO) films, monocrystals, and polycrystals and for Nb films. The most distinctive feature of the temperature dependence P3(T) of nonlinear response of superconductors is a maximum of the nonlinearity near the critical temperature Tc. Spatial distributions of the third-harmonic power are obtained for YBCO films at various temperatures. These distributions are indicative of a nonuniform distribution of Tc over the superconductor surface. Additional nonlinearity maxima are discovered in the dependence P3(T) for YBCO films and monocrystals at temperatures about 2Tc/3. These maxima are probably related to the existence of several superconducting phases with different critical temperatures. For Nb films, the second nonlinearity maximum in the dependence P3(T) appears only in the presence of an external magnetic field. The experimental data are interpreted within the framework of a two-fluid model of a superconductor, which takes into account the phenomenological nonlinear relationship between the vector potential A and the supercurrent js(A). The origin of nonlinearity in the studied superconductors is discussed.  相似文献   
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8.
Terahertz and infrared spectra of the conductivity, σ(ν), and dielectric constant, ?(ν), of a Ba(Fe0.9Co0.1)2As2 film (T c = 20 K) have been analyzed together with previous specific-heat and angular resolved photoelectron spectroscopy data. It has been shown that the spectra σ(ν) and ?(ν) of Ba(Fe0.9Co0.1)2As2 in the superconducting phase at T = 5 K, as well as the magnetic field penetration depth, can be described well using the standard Bardeen-Cooper-Schrieffer (BCS) model with an additive contribution of electron and hole bands. It has been found that the measured temperature dependence of the magnetic field penetration depth in a wide temperature range 5 K < T < T c can be described only with the introduction of interband pairing interaction. The coupling constant of electron and hole bands, λ1, 2 = 0.1, as well as the temperature dependences of superconducting gaps in the electron and hole subsystems, has been determined using the model of two-band superconductivity developed earlier for MgB2.  相似文献   
9.
The local nonlinear microwave response of YBa2Cu3O7 ? x films was measured by near-zone field microscopy with a spatial resolution of 50 μm, and YBa2Cu3O7 ? x film microbridges were locally studied by low-temperature scanning microscopy with a spatial resolution of 4 μm. The microstructure of epitaxial YBa2Cu3O7 ? x films was examined using x-ray diffraction and electron microscopy. A correlation is detected between the average crystallite size and the half-widths of the temperature dependences of the third-harmonic power (W TH) and the electron-beam-induced voltage (W EBIV). The experimental results are described in terms of a model of a two-phase medium taking into account the nonlinear I-V characteristic of the superconductor. For large crystallites, the nonlinear microwave response is shown to be caused by intracrystallite vortex pinning. As the average crystallite size decreases, an additional contribution to the nonlinear response appears due to the pinning of a magnetic flux by the Josephson network of crystallite boundaries. Calculations show that a three-fold increase in the crystallite size decreases the nonlinearity coefficient of YBa2Cu3O7 ? x films by two orders of magnitude.  相似文献   
10.
Magnetic field measurements above type-II superconductor films in a remanent magnetization state have been used to determine two dimensional surface current distributions. Using the Biot-Savart law for the surface current density, integral equations (of 2-D convolution type) for two components of current have been obtained. These equations have been solved by employing Tikhonov's method of generalized discrepancy, and the surface current pattern in superconductors as well as the magnetic field distribution on the film surface have been obtained. Current peculiarities related to various kinds of inhomogeneities, specific character of the film form, and a laser pulse effect have been observed. In particular, it was discovered that a laser pulse can signficantly redistribute the film currents without changing the total number of current vortices in the film.  相似文献   
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