Magnetic Interaction Force Research Articles

Cohesion induced by a rotating magnetic field in a granular material.

We report experiments on a magnetic cohesive granular material made of steel spheres in the millimeter range. A magnetic field magnetizes the spheres, so that an interaction force between grains appears. A rotating magnetic field is applied parallel to plane of the quasi-two-dimensional cell containing the spheres so that only the time averaged force between two particles will be considered. Both maximum angle of stability and angles of repose are measured. The maximum angle of stability is found to depend linearly on the interaction force. Another noticeable feature is the lack of dependence of the maximum angle of stability on the initial height of the heap. We show that the angle of repose is less sensitive to the magnetic interaction force than the maximum of stability. At last, we discuss the importance of using a rotating field rather than a constant one. In particular, we report some measurements of both the maximum angle of stability and the angle of repose in constant field, which show a strong dependence of the angles of avalanche on the direction of the field.

자기력과 Random Fluidic Self-assembly에 의한 신규 바이오칩의 개발

This paper describes a new constructing method of multifunctional biosensor using many kinds of biomaterials. A metal particle and an array was fabricated by photolithographic. Biomaterials were immobilized on the metal particle. The array and the particles were mixed in a buffer solution, and were arranged by magnetic force interaction and random fluidic self-assembly. A quarter of total Ni dots were covered by the particles. The binding direction of the particles was controllable, and condition of particles was almost with Au surface on top. The particles were successfully arranged on the array. The biomaterial activities were detected by chemiluminescence and electrochemical methods.

Measuring Magnetic Field Saturation and its Site Dependence in a Recording Head With a Magnetic Force Microscope

We directly imaged magnetic field saturation from the gap corners of a recording head by using magnetic force microscopy (MFM). We measured the magnetic force interactions associated with the variation of the magnetic field with respect to the applied current with high spatial resolution and studied the site dependence of the saturation behavior of the head. Our experiments show that the magnetic field saturation starts at current values as low as 3 mA at the gap edge corners of the head, while the gap edge center saturated at about 10 mA.

408 多数振動子における振動パターン(同期化・パターン形成,OS-6 パターン形成現象と複雑性)

This paper describes the experimental results and calculated ones on synchronized phenomena of oscillators weakly coupled by magnetic force. Two permanent magnets are attached to the arms of pendulum. The pendulum is affected by the force of attraction or repulsion. As the results of the magnetic force interaction, in-phase synchronization and out-of-phase synchronization are observed. The type of synchronization depends on the potential energy of magnetic forces.

Numerical simulation of coupled problem of electromagnetic field and heat conduction in superconducting magnetic bearing

Abstract The superconducting magnetic bearing (SMB) system consists of the HTSC stator and the PM rotor, and is a no-contact bearing system using the levitation force between them. The SMB was expected to be applied to the electric power storage flywheel system because no friction causes the rotation speed degradation and decreases the energy storage capability. However, it was found that the electromagnetic friction of the SMB was not zero, due to electromagnetic forces; (1) the magnetic force interaction between the inhomogeneous magnetic field of the PM rotor and the eddy current it induces in the cryostat, (2) the magnetic force between the inhomogeneous magnetic field of the PM rotor and the shielding current it induces in the superconductor, (3) the magnetic force between the magnetic field of superconductors yielding the levitation force and the eddy current induced in the PM rotor. The magnetic field of superconductor is inhomogeneous too, because the superconductors consist of several HTSC bulks. We improved the PM rotor and succeed in suppressing the rotation speed degradation by inhomogeneous magnetic field of HTSC bulks by preventing the eddy current with many insulator thin films in the PM rotor [Trans. Supercond. (in press)]. On the other hand, the rotation speed degradation by inhomogeneous magnetic field of the PM rotor have not been able to be removed. The induced eddy currents generate temperature rise with Joule heat in HTSC bulks. Therefore we are able to estimate the rotation speed degradation by evaluating the temperature rise. Furthermore temperature rise can cause inhomogeneous magnetic field because physical properties is varied by it. The purpose of this research is to develop the electromagnetic field analysis method coupled with thermal analysis.

Numerical and experimental analysis of the rotation speed degradation of superconducting magnetic bearings

The suppression of the rotation speed degradation of the Superconducting Magnetic Bearing (SMB) with the Permanent Magnet (PM) rotor including the layered insulator thin films is studied. The SMB system consists of the superconductor stator and the PM rotor, and is a no-contact bearing system using the levitation force between them. The SMB was expected to be applied to the electric power storage flywheel system because friction causes the rotation speed degradation and decreases the energy storage capability. However, it was found that the electromagnetic friction of the SMB was not zero, due to electromagnetic forces; 1) the magnetic force interaction between the inhomogeneous magnetic field of the PM rotor and the eddy current it induces in the cryostat, 2) the magnetic force between the inhomogeneous magnetic field of the PM rotor and the shielding current it induces in the superconductor, 3) the magnetic force between the magnetic field of superconductors yielding the levitation force and the eddy current induced in the PM rotor. This magnetic field of superconductor is inhomogeneous too, because the superconductors consist of several HTSC bulks. In this research, it was found that the 3rd phenomenon is most significant. So, we use the advanced PM rotor including the layered insulator thin films to suppress its eddy current and the degradation of the rotation speed. Using our SMB equipment, the rotation speed degradation was measured using the PM rotors with/without the insulator thin films and the electromagnetic frictions were compared to each other.

Magnetic interaction force between high-Tc superconductor-ring and magnet

The magnetic interaction force between superconducting ring and cylindrical permanent magnets of different lengths, aligned coaxially, has been investigated experimentally at zero-field-cooled and field-cooled conditions. The force as a function of the position of the magnet relative to the superconductor ring is qualitatively that expected if the superconductor is regarded as a diamagnet with nonohmic dissipation. The hysteretic behavior of the axial force component was studied. It is shown that the size of the hysteresis loop grows with the strength of the magnet in general, but the shape of the loop also undergoes complicated changes. It was found that field-cooled conditions can yield a higher support force in this permanent magnet and superconducting ring system, with lower hysteresis loss. This makes this system an attractive candidate for a low loss magnetic journal bearing.

Immobilization of Biomaterial by Random Fluidic Self-Assembly Method

We propose a novel method for individual immobilization of biomaterial for biosensor application. Various kinds of biomaterial were first immobilized on certain supports such as glass beads or microfabricated metal particles of which size is almost the same as the size of transducer element. Then the suspension mixture of the various support was arranged on the transducer array by the fluidic self-assembly method at random. Glass beads immobilized with glucose oxidase and/or peroxidase were successfully arranged by this method using gravity, as a short-range force required in self-assembly. The beads gave chemiluminescence with the addition of luminol and its substrate. The metal particles consisted of nickel and/or gold layers formed by electroplating and evaporation on a photolithographically patterned chip. The coin-shaped particles were arranged on a nickel dot array by magnetic force interaction as the short-range force. The direction of binding of the particles were also controllable using the multilayer structure.

Y2BaCuO5 excess and quenching influences on melt-textured YBCO

We investigated the influence of the preliminary heat treatments of precursor oxides (calcination and/or quenching) and their stoichiometries (various amounts of Y2BaCuO5 (Y-211) phase excess) on the melt-textured growth of YBCO samples. We tried to correlate the process parameters with the obtained microstructures and the exhibited superconducting properties at 77 K, i.e. magnetic interaction forces as a function of the distance from a permanent magnet and magnetization hysteresis at different applied magnetic fields. The results revealed the positive effects of Y-211 phase excess (20% molar) and of quench treatment of BaO2+CuO precursor oxides. We found the importance of fine and homogeneous Y-211 residual particle distribution, which is favoured both by adding an excess of Y2O3 powder instead of Y-211 preprepared powder and by the introduction of a quench treatment before the growth process. We analysed materials produced with different quenching conditions of precursor powders in order to optimize the process. Magnetization critical current densities of 2.2*104 A cm-2 and 1.4*104 A cm-2 were evaluated at 77 K with 0.1 T and 1 T fields applied parallel to the sample c axis.

Magnetic coupling in superposed type-II superconducting films

A study has been made of the magnetic-coupling properties of vortex arrays in a dc superconducting transformer composed of two oxygen-doped aluminum films separated by a thin insulating layer. By doping to the appropriate level, very small depinning currents have been achieved, making possible an investigation of the vortex-coupling characteristics in a low-current regime free of heating instabilities. Measurements of the system's $V\ensuremath{-}I$ characteristics have been obtained at currents more than an order of magnitude greater than the current at which the two vortex lattices cease to move at the same velocity. A simple periodic-coupling-force model has been used to generate theoretical $V\ensuremath{-}I$ curves which are found to compare well with the experimental data. Values of the magnetic interaction force coupling the two vortex arrays have been determined as a function of temperature and intervortex spacing, and are compared with theory.