We demonstrate the microwave detection effect in a granular La0.7Ca0.3MnO3 sample. Dc voltage generated by the sample in response to microwave irradiation below the Curie temperature is found to be ...dependent on the applied magnetic field. The magnetic field dependence of the dc voltage has a broad peak resembling an absorption line. The detection effect depends substantially on the magnetic history of the sample; however, identical measurement conditions provide reproducibility of the experimental results. The detected dc voltage increases linearly with microwave power and strongly depends on a bias current through the sample. According to the results of systematic measurements, there exist two contributions to a value of the detected output signal. The first is magneto-independent; it can be explained in the framework of a mechanism used traditionally for description of the rectification effect in metal-insulator-metal junctions with nonmagnetic metals. The other is magneto-dependent; it originates from the interplay between the spin-dependent current through magnetic tunnel junctions and spin dynamics of the grains, which form these junctions in the sample.
The broadening of the resistive transition in magnetic field and isotherms of magnetoresistance of bulk composites Y–Ba–Cu–O + CuO have been studied. These composites exhibit large magneto-resistive ...effect in a wide temperature range below
T
C
due to weakening of Josephson coupling in this system. The broadening of the resistive transition and magnetoresistance are explained well by the Ambegaokar–Halperin (AH) model for phase slip in Josephson junctions. The magnetic field dependence of pinning potential in the intergrain boundaries deduced from AH model found out to be similar to that of critical current of an array of Josephson junctions. The values of pinning energy point out that the large magneto-resistive effect observed in the composites results from flux flow-like processes at the intergrain boundaries.
Results of screening studies of the sorption of naturally occurring biologically active compounds (phenolcarboxylic acids, coumarins, flavonoids, and alkaloids) on aluminum- and iron-containing ...metal-organic frameworks (MOFs) are presented. The structures of the synthesized MOFs were characterized by powder x-ray diffraction, porosimetry, and ATR-FTIR spectroscopy. Sorption of the analytes was quantitatively analyzed by UV spectrophotometry. The sorption activity of iron-containing MOFs was determined to be higher than that of aluminum-containing MOFs. The difference in sorption capacities indicates that targeted selection of MOFs for selective retention or separation of a mixture of chemically different substances is possible.
Modern electromagnetic actuators, in particular proportional solenoids, are complex mechatronic systems, including both an actuator and its control system. Electromagnetic actuators are often used in ...control systems of increased liability and therefore continuously evolving. The development of new types of electromagnetic actuators is based on experimental configuring of parameters of regulators and comprehensive product testing. The complexity and the continuous improvement of the currently used magnetic systems require new approaches to the management of high-precision position of the movable elements. This article discusses an integrated approach to research, monitoring, diagnostics and control of DC proportional solenoids. This approach is based on sensorless measuring of the complex flux-ampere characteristics of the electromagnetic system employed detecting malfunctions, and for determining the position of the movable drive member.
The intragrain pinning in high-Tc superconductor compounds Y1-xRExBa2Cu3O7-delta with low concentration of RE (La, Ce, Pr) was investigated. Magnetic and transport measurements reveal that the ...pinning is maximal for the concentration of heterovalent RE such that the average distance between the impurity ions in the plane of rare-earth elements is close to the diameter of Abrikosov vortices in YBCO.
The magnetoresistance (MR) of substituted lanthanum manganite (La
0.5
Eu
0.5
)
0.7
Pb
0.3
MnO
3
has been measured in a pulsed magnetic field with amplitude
H
= 250 kOe at various temperatures. It is ...established that temperature dependence of the MR relaxation parameter τ(
T
) is correlated with temperature dependence of the electric resistance
R
(
T
). A mechanism of relaxation is proposed that is related to the relaxation of conducting and dielectric phases in the volume of a sample under the conditions of phase separation. It is shown that the behavior of τ is related to the number of phase boundaries in the volume.
In the production of electrical products, an important element is conducting exit and intermediate control operations to reduce risks. A promising approach to the diagnosis of electromagnetic devices ...is the analysis of their weber-ampere characteristics. Control of the magnetic properties of products allows identifying defects without the need for long-term operations of disassembly / assembly mechanisms. The introduction of sensors of magnetic magnitudes into the design of electromagnets is impractical in terms of cost and reliability. With the help of the "working" elements of electromagnets already available in the design, it is possible to measure the weber-ampere characteristics. The article solves the problem of analysis and identification of the relationship between the critical defect of armored-type electromagnets with the weber-ampere characteristic of the product and the development of a method for the technical diagnosis of a malfunction.
The dependence of magnetization on magnetic field M(H) was measured for textured BSCCO samples in directions H‖c,H‖ab at different temperatures. Inclusion of the pinning parameter in the ...Valkov–Khrustalev model V.V. Valkov, B.P. Khrustalev, JETP 80 (1995) 680 allowed to describe successfully the asymmetric M(H) dependencies. The temperature and magnetic field dependencies of critical current and pinning parameter for H‖c and H‖ab were estimated.
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