Strong Permanent Magnet Research Articles

Imaging of Magnetic Data Bits and Ferromagnetic Domains with Photoelectron Emission Microscopy

Magnetic data bits recorded on a computer hard drive disk and ferromagnetic domains on a sample of neodymium–iron–boron, Nd 2 Fe 14 B , a material used in strong permanent magnets, are imaged using an electrostatic photoelectron emission microscope. Local stray magnetic fields of opposite orientation, which exist above the data bits and above ferromagnetic domains, laterally deflect photoelectrons emitted from the samples and partially split the photoelectron beam into two directions. Magnetic contrast is achieved by blocking part of the photoelectron beam with the edge of an aperture. The binary code of a magnetic storage disk is read directly. Disappearance of ferromagnetic domains is followed in real time as Nd 2 Fe 14 B is heated above its Curie temperature. The spontaneous reappearance of ferromagnetic domains is seen as Nd 2 Fe 14 B is cooled.

Stability considerations of permanent magnet quadrupoles for CESR phase-III upgrade

The Cornell electron storage ring (CESR) phase-III upgrade plan includes very strong permanent magnet quadrupoles in front of the cryostat for the superconducting quadrupoles and physically as close as possible to the interaction point. Together with the superconducting quadrupoles, they provide tighter vertical focusing at the interaction point. The quadrupoles are built with neodymium iron boron (NdFeB) material and operate inside the 15 kG solenoid field. Requirements on the field quality and stability of these quadrupoles are discussed and test results are presented.

Field design studies of a planar hybrid/permanent magnet undulator with strong planar permanent magnet focusing

Undulators for Free Electron Laser (FEL) amplifiers driven by multi-GeV electron beams generally require superimposed focusing substantially stronger than that provided by their natural focusing fields. In recent years a wide variety of focusing schemes and configurations have been proposed for undulators of this class, ranging from conventional current-driven quadrupoles external to the undulator magnets to permanent magnet (PM) lattices inserted into, or adjacent to, the insertion device gap. In this paper we present design studies of the field structure of a flexible hybrid/PM undulator with superimposed planar PM focusing proposed for a 1.5 Å Linac Coherent Light Source (LCLS) undulator driven by an electron beam with a 1 mm mrad normalized emittance. Attainable field parameters, tuning modes, and trajectory performance of the proposed structure are discussed.

Studies on combination for high-Tc superconducting permanent magnets

For the purpose of studying the feasibility of the bulks combination for a strong permanent magnet, a HTS permanent magnet in the cuboid shape was constructed of MTG-YBCO bulks and the corresponding asymmetric spatial flux distribution of a remanent state seems to be rather inhomogeneous. It was found experimentally that well-designed high permeability materials is helpful to enhance the magnetic stability and make the flux distribution uniform. The movement among the HTS bulks with trapped fluxes would give rise to magnetic energy losses, which is analogous to the training effect in superconducting magnets.

磁性スラリーによる硬ぜい性材料の精密研磨（ＦＦＦ） 磁場可変の効果

Magnetic field-assisted fine polishing method has been proposed, which uses a magnetic slurry mixed non-ferrous abrasives into a magnetic fluid. Polishing machine has newly been developed which is consisted both of copper rotary disc set a strong permanent magnet and a rotary shaft set similar one, it is mounted a specimen to be polished. Magnetic field strength controlled by moving their magnets is responsible for yielding superior surface quality. It is found that polishing machine has high performance finishing ability and the usage of a variety of magnetic fluid is proposed versatile polishing characteristics. Experiments show that kerosene based magnetic fluid has very high polishing performance compared with water based one. The usage of coarse grain gives rise to increase the surface roughnes, and larger clearance between specimen and copper rotary disc lowers finishing rate of wafer in kerosene based magnetic fluid especially. Movement of permanent magnet in copper rotary disc is very effective for finishing of wafer.

High Sensitive Portable ESR Spectrometer for Radiation Dosimetry.

Using the strongest permanent magnet (NEOMAX), a high-sensitive portable ESR spectrometer useful for practical measurements has been developed. The spectrometer is assembled in one small case with the weight of about 25 kg and is operated by a personal computer. The spectrometer reaches a sensitivity of 2×1010 spins/0.1 mT with a resolving power below 0.045 mT. This spectrometer can be utilized for practical measurements and fundamental researches. An important field of practical measurements is the dosimetry of gamma radiations. The spectrometer is also to characterize the alanine samples irradiated from 10 Gy to 30 kGy with an accuracy of scattering lower than 2%.

A compact Penning trap for light ions

We describe the construction of a novel compact Penning trap from strong permanent magnets for trapping light ions. Our cylindrically symmetric, iron-free magnetic configuration allows fully analytical treatment, is easy to handle and to optimize. The magnetic field inhomogeneity is less than 1% in a volume of 1 cm3 at 0.7 T. The stored H+ and H 2 + ions in this trap are detected electrically by the rf absorption method. The charge density, total number and storage time of the trapped ions are measured.

Remanent induction and levitation force of melt textured YBCO

Bulk cplindrical pBCO blocks up to 5 cm in diameter are fabricated bp a modified melt texturing process. The multi-domain material pith domain sipes of about 1 cm 3 shops a c-axis texture correlated pith the temperature gradient during the gropth process. Motivated bp the potential of material for applications as strong permanent magnets or in field trapping devices, pe studied the application relevant magnetic properties. puasi-single crpstalline domains pere extracted from the blocks and cut into cubes, cplinders, and discs pith pell-defined crpstal orientation. The anisotropic intra-domain magnetic properties of these samples are measured bp vibration sample magnetometrp. Trapped inductions are calculated from the measured remanent magnetic moments m rem assuming a homogeneous magnetipation distribution in the sample. For a disc pith 4 mm diameter 2 T at 20 K and 4 T at 4.2 K trapped inductions are estimated. Flux jumps in the magnetipation loop are observed at 4.2 K. Flux trapping parallel to the c-axis is dominant but also trapping parallel to the ab-planes occurs in a near angular range. The anisotropp ratio is m rem//ab = 1 3 m rem//c at 77 K. Sample shape effects on the flux trapping cannot be neglected. To characteripe the material properties that are relevant for levitation applications a 3D positioning spstem pith piepo force sensors respective Hall probes pas constructed. puasi-static measurements of the major and minor force-position loops in the pero field cooled and field cooled state are performed. The pBCO blocks are tested in a demonstration model of an electromotor pith the shaft free rotating supported bp a hpbrid superconducting bearing up to 7000 rpm. The application in a field trapping device is tested bp using the material as a rotor of a 15 p hpsteresis electromotor.

Pure multipoles from strong permanent magnets: analytic and experimental results

We present the construction of arbitrary multipole field configurations from strong permanent magnets for trapping charged or neutral particles. A general analytic method for the design of three-dimensional magnetic multipoles is discussed for an idealized continuously varying magnetisation taking advantage of the superposition principle. Simple recipes for constructing magnetic dipole and quadrupole fields are given with two types of elements, axially and radially magnetised rings. Cylindrical magnet components not only give free access to the experimental region of interest, but also allow for some tunability to reduce undesirable higher multipole orders. Measurements confirm theoretical predictions achieving useful magnetic fields of 1 T and steep gradients of 3 T/cm with high purity over several ccm.

Relation between magnetically-applied force and velocity in beads coated with rabbit myosin, sliding on actin cables in Nitellopsis cells

We have succeeded in controlling the sliding movement of myosin-coated magnetizable beads on actin cables in Nitellopsis cells by the inhomogeneous magnetic field adjacent to a small, strong permanent magnet. The relation between magnetic force acting on the bead and the bead velocity was, in many respects, similar to that obtained from the same system by the use of centrifugal force (Oiwa et al., 1990). In particular, force favouring the motion (negative load) had little effect on the velocity until it was sufficient to pull the bead off the actin, whereas a relatively small positive load caused a reduction in velocity to a plateau value. Although the present method does not allow a good control of force direction, it demonstrates the promise of magnetic force in studying in vitro motility.

Magnetic properties of superconducting YBa2Cu3Ox permanent magnets prepared by the melt process

Demagnetizing curves after field cooling were measured in the melt processed YBa2Cu3Ox superconductors using a vibrating sample magnetometer and a SQUID magnetometer. The curves showed that the samples worked as strong bulk permanent magnets. This is attributed to the strong flux pinning of the bulk superconductors and is well explained in terms of the Bean–London model. The magnetic properties of the permanent magnet can be continuously changed using the field-cooling technique. The magnet properties of the melt-powder–melt-growth processed YBa2Cu3Ox with 1.5 mm thickness obtained at 5 K after field cooling in 10 kOe are as follows: the residual flux densities Br are 9.6 kG (H∥ c) and 8.5 kG (H⊥ c); the coercive forces bHc are 33 kOe (H∥ c) and 17 kOe (H⊥ c); and the maximum energy product, (BH)max, are 110 MGOe (H∥ c) and 49 MGOe (H⊥ c).

Magnetism of nanostructured rare earth multilayers and films

A review is given of recent research on amorphous, compositionally modulated rare earth—transition metal films. Factors determining their magnetic structure, perpendicular magnetic anisotropy and magneto-optic properties are discussed. Thin films of rare earth—transition metal compounds which have strong permanent magnet properties are outlined. Many of the new complex compounds have been prepared as thin films with controlled anisotropies. Possible applications of such films are briefly discussed.

Magnetic properties of superconducting permanent magnets of YBa2Cu3Ox

Abstract DC magnetic properties were measured in the melt processed YBa2Cu3Ox after field-cooling using a SQUID magnetometer. The magnetic properties estimated from the demagnetizing curves showed that the samples worked as strong bulk permanent magnets. This is attributed to the large pinning forces obtained in the bulk superconductors. The dependence of the magnet properties on the applied fields in field-cooling indicates that the properties can be continuously changed using the field-cooling technique. The magnet properties of the Melt-Powder-Melt-Growth processed YBa2Cu3Ox with 1.5mm thickness obtained at 5 K after field-cooling in 10 kOe (H//c) are as follows: the residual flux density, Br is 9.6kG, the coercive force, bHc is 33kOe and the maximum energy product, (BH)max is 110MGOe.

Analysis of a Permanent Magnet Levitation Actuator With Electromagnetic Control

This paper proposes an actuator in the magnetic levitation system using a permanent magnet and an electromagnet. In this system, the gravity force of the masses is supported by a strong permanent magnet in which two identical poles face each other. The vibration due to external disturbances is controlled by use of the electromagnet by changing magnetic fluxes of one of the permanent magnets. The analytical expressions for obtaining the levitation force, spring constant, and the control force versus the electric current in the electromagnet were derived using the equation of the electromagnetic theory. Numerical simulations under the control using the optimal regulator for the magnetically levitated body were carried out. To verify the present theoretical results, experimental results were also obtained.

Magnetization Properties of YBaCuO Prepared by Quench and Melt Growth Process

DC magnetization measurements were carried out on YBaCuO prepared by the quench and melt-growth (QMG) process using a vibrating sample magnetometer and a SQUID magnetometer below 100 K. It was found that the DC magnetization behavior of QMG-grown YBaCuO at 4.2 K can be quantitatively explained in terms of Bean's critical state model. This sample also can become a strong bulk permanent magnet with an energy product of more than 80 MGOe at 5 K because of its strong pinning force.

Heart catheterization in a neonate by interacting magnetic fields: A new and simple method of catheter guidance

Catheter guidance in a critically ill neonate can be difficult and hazardous. A new technique of directing a catheter based on the interaction of magnetic fields is described. A strong external permanent magnet is moved across the body surface to control the magnetic tip of a catheter in the body. We report on the first clinical case of such a heart catheterization in a neonate with complex congenital heart disease. This method can also be used for other invasive investigations in the neonatal period.

Magnetization study of YBaCuO prepared by quench and melt growth process

D.C. magnetization measurements were carried out on YBaCuO prepared by the quench and melt growth(QMG) process using a vibrating sample magnetometer and a SQUID magnetometer below 77K. It was found that the D.C. magnetization behavior of QMG processed YBaCuO at 4.2 K can be quantitatively explained in terms of Bean model. This sample also can become a strong bulk permanent magnet with a maximum energy product exceeding 80MGOe at 5 K due to its large pinning force.

A magnetic-levitation actuator using a permanent magnet and an electromagnet and its application to active control of a magnetic-levitated body.

This paper proposes an actuator in the magnetic levitation system using a permanent magnet and an electromagnet. In this system, the gravity force of the masses is supported by a strong permanent magnet in which two identical poles face each other. The vibration due to external disturbances is controled by use of the electromagnet by changing magnetic fluxes of one of the permanent magnets. The analytical expressions for obtaining the levitation force, spring constant and the control force versus the electric current in the electromagnet were derived using the equation of the electromagnetic theory. Numerical simulations under the control using the optimal regulator for the magnetically levitated boby were carried out. To verify the present theoretical results, experimantal results were also obtained.

溶融法で作製したＹＢａＣｕＯの磁化特性

D.C. magnetization measurements were carried out on YBaCuO prepared by the quench and melt growth (QMG) process using a vibrating sample magnetometer and a SQUID magnetometer below 100 K. It was found that the D.C. magnetization behavior of QMG processed YBaCuO at 4.2 K can be quantitatively explained in terms of Bean‘s critical state model. This sample also can become a strong bulk permanent magnet with an energy product of more than 80 MGOe at 5 K because of its strong pinning force.

IS THE MAGNETIC SUSPENSION OF HIGH-TEMPERATURE SUPERCONDUCTORS A GENERAL PHENOMENON?

We have observed that all high-T c superconductors like RE Ba 2 Cu 3 O 7, Bi-Ca-Sr-Cu-O and Tl-Ca-Ba-Cu-O can be suspended below a strong permanent magnet. The magnetic suspension in high-temperature superconductors is obviously a general phenomenon, i.e., it is not restricted to samples of YBa 2 Cu 3 O 7 doped with silver oxide as suggested in literature.