Magnetic field and its gradient measurements based on coherent population trapping resonances at the D_1 line of ^{87}Rb are performed by means of coupling two ground-state Zeeman sublevels belonging to different hyperfine levels to a common excited state. Two coherent laser fields with frequency difference of 6.8 GHz are used. They are produced by direct current modulation of a diode laser. The resonance splitting and broadening caused by the applied magnetic field is measured by scanning the laser modulation frequency around the ground-state hyperfine frequency.
The paper presents numerical model and validation of new methodology of offset voltage minimization in the Hall-effect sensors. Model of the Hall-effect sensor with multiple electric pins was developed. Mathematical equations used for calculation of electric potential difference were formulated. Simulations were carried out using finite elements method in ELMER FEM software. Performed investigation of actual parameters of newly designed Hall-effect sensor confirms effectiveness of the described method.
This paper presents innovative isolated DC and AC current amplifier containing magnetic field sensor in the feedback loop. The amorphous ring core with an air gap is utilized as a part of the galvanic isolation separating input and output currents. In the paper outline of the amplifier is presented. The printed circuit board project was developed and electronic circuit of the amplifier was manufactured. The developed device was investigated with DC and AC current and the results are presented in the paper. Results indicate usefulness of the developed device in described application.
Small values of external perturbation forces made it possible to use a torque magnetic drive as a control system. Today, satellite orientation systems use pulsed-type algorithm for discharge of an angular momentum accumulator. The feasibility of using other algorithms (continuous, continuous-pulsed and algorithm of torque magnetic drive operation using `forecast' models of accumulated angular momentum and geomagnetic field) is not covered and not examined, although each has certain advantages for certain types of satellites and their conditions of operation in space. The article highlights satellites operating conditions in space, considers satellites orientation method using a torque magnetic drive and substantiates the necessity of satellite motion simulation with further establishing a technique for evaluation of orientation system given the effect of permanent magnetic and gravitational fields, the type of discharge of accumulated angular momentum, the height of trajectory and the nature of random perturbations.
Tomography is a useful tool for objects reconstruction in non-destructive testing. Many kinds of tomography, depending on the penetrating wave character, are available and adapted for specific application. This paper presents new kind of tomography - conductance tomography extended with a Hall effect. Its development was motivated by the need on inhomogeneity detection in thin film Hall effect sensor, particularly graphene Hall effect sensors. Paper presents complete description of the tomographic method and tomography software developed in the GNU Octave. Inverse transformation is based on optimization method. Each shape reconstruction was done with the finite element method using the open source software: Elmer FEM and Salome. Results confirmed the suitability of the work.
The article constitutes the continuation of the works realized under the research project entitled: "The development of the method for marking and identification of the spots dangerous and of special importance for vision impaired persons in the big city with use of the wave-vibration markers". The consideration included the identification of the object (human), identification of the direction of movement (double barrier), wireless data transmission with the information on the dangerous area, stimulation of the vibration signal and the feedback of the system. This article presents the result of choice of the optimal solution regarding the installation of the system on the selected objects of the urban engineering and also presents the concept of the method of modelling of the shape of the zone that is used for marking of the dangerous spot.
Colossal magnetoresistance effect B-scalar magnetic field sensors with effective areas of 0.05 mm^2 were used very close to the rails for magnetic field measurements. These measurements were performed during static and dynamic railgun experiments. In static experiments three different rail materials were used and the results are compared to a finite element simulation.
In this paper we present the effect of the thickness on the field-induced anisotropy of NiFe layers. We electroplated several ring-cores with thickness spanning from 2 μm to 18 μm changing the deposition time (and keeping unchanged the other parameters). The ring-cores were placed during the electroplating process in yoke, which produced 720 kA/m radial field in order to induce a radial anisotropy to the ring. We observed that the field-induced anisotropy significantly increases up to 12 μm thickness; for further increment of thickness the anisotropy does not increase anymore. The effect is visible on the noise of the fluxgate based on such rings: the noise quickly drops for increase of thickness due to larger radial anisotropy. However, for 18 μm the noise slightly rises due to emerging of demagnetizing effect. Therefore we derive that 12 μm is the best trade-off between the need of larger field-induced anisotropy and low demagnetization.
In order to advance modern information technologies, progress in both the fabrication of magnetic nanostructures and of complex materials, from which small magnetic entities - like the skyrmions present in MnSi - emerge and in developing measurement techniques are desired. Here the sensor-based stray field detection using tailor-made micro-Hall magnetometers has proven to be a versatile tool for studying the magnetization reversal of individual magnetic nanostructures, domain wall motion in thin films, as well as the local stray field close to macroscopic samples. In this article we demonstrate that the local stray field can be used to accurately map out the B-T phase diagram of MnSi and serve as a guidance for simultaneously-performed electronic transport measurements. The presented study also serves as a proof-of-principle experiment for future combined investigations of electronic transport and magnetization focusing on electrically-contacted magnetic nanostructures.
The paper presents results of research on the effects of mechanical stresses on the magnetostrictive properties of 13CrMo4-5 steel. Measurements of stress dependence of magnetostriction fill the gap in the state of the art enabling description of relationships between stresses applied to the samples and its magnetoelastic and magnetostrictive properties. Performed studies represent the starting point for development of unified model of both Villari (magnetoelastic) and Joule (magnetostrictive) effects under stresses in steels. The formulated model will be the basis for the development of generalized methods of interpreting the results of non-destructive testing of the state of the internal stresses in steels based on these phenomena.
The paper describes the design, development, and investigation of a new type of Hall-effect sensors of a magnetic field made of graphene. The epitaxial growth of high-quality graphene structures was performed using a standard hot-wall CVD reactor, which allows for easy integration with an existing semiconductors production technologies. The functional properties of developed Hall-effect sensors based on graphene were investigated on special experimental setup utilizing Helmholtz coils as a source of reference magnetic field. Monolayer and quasi-free-standing bilayer graphene structures were tested. Results presented in the paper indicate that graphene is very promising material for development of Hall-effect sensors. Developed graphene Hall-effect sensor exhibit highly linear characteristics and high magnetic field sensitivity.
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