skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Permanent magnet with MgB{sub 2} bulk superconductor

Abstract

Superconductors with persistent zero-resistance currents serve as permanent magnets for high-field applications requiring a strong and stable magnetic field, such as magnetic resonance imaging. The recent global helium shortage has quickened research into high-temperature superconductors (HTSs)—materials that can be used without conventional liquid-helium cooling to 4.2 K. Herein, we demonstrate that 40-K-class metallic HTS magnesium diboride (MgB{sub 2}) makes an excellent permanent bulk magnet, maintaining 3 T at 20 K for 1 week with an extremely high stability (<0.1 ppm/h). The magnetic field trapped in this magnet is uniformly distributed, as for single-crystalline neodymium-iron-boron. Magnetic hysteresis loop of the MgB{sub 2} permanent bulk magnet was determined. Because MgB{sub 2} is a simple-binary-line compound that does not contain rare-earth metals, polycrystalline bulk material can be industrially fabricated at low cost and with high yield to serve as strong magnets that are compatible with conventional compact cryocoolers, making MgB{sub 2} bulks promising for the next generation of Tesla-class permanent-magnet applications.

Authors:
 [1];  [2]; ;  [3];  [1]
  1. The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan)
  2. (Japan)
  3. Railway Technical Research Institute, 2-8-38 Hikari, Kokubunji, Tokyo 185-8540 (Japan)
Publication Date:
OSTI Identifier:
22311152
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 3; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BORON COMPOUNDS; CURRENTS; HIGH-TC SUPERCONDUCTORS; HYSTERESIS; IRON COMPOUNDS; MAGNESIUM BORIDES; MAGNETIC FIELDS; MONOCRYSTALS; NEODYMIUM COMPOUNDS; NMR IMAGING; PERMANENT MAGNETS; POLYCRYSTALS; SHORTAGES; STABILITY; TEMPERATURE RANGE 0013-0065 K; TRAPPING

Citation Formats

Yamamoto, Akiyasu, E-mail: yamamoto@appchem.t.u-tokyo.ac.jp, JST-PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Ishihara, Atsushi, Tomita, Masaru, and Kishio, Kohji. Permanent magnet with MgB{sub 2} bulk superconductor. United States: N. p., 2014. Web. doi:10.1063/1.4890724.
Yamamoto, Akiyasu, E-mail: yamamoto@appchem.t.u-tokyo.ac.jp, JST-PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Ishihara, Atsushi, Tomita, Masaru, & Kishio, Kohji. Permanent magnet with MgB{sub 2} bulk superconductor. United States. doi:10.1063/1.4890724.
Yamamoto, Akiyasu, E-mail: yamamoto@appchem.t.u-tokyo.ac.jp, JST-PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Ishihara, Atsushi, Tomita, Masaru, and Kishio, Kohji. 2014. "Permanent magnet with MgB{sub 2} bulk superconductor". United States. doi:10.1063/1.4890724.
@article{osti_22311152,
title = {Permanent magnet with MgB{sub 2} bulk superconductor},
author = {Yamamoto, Akiyasu, E-mail: yamamoto@appchem.t.u-tokyo.ac.jp and JST-PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 and Ishihara, Atsushi and Tomita, Masaru and Kishio, Kohji},
abstractNote = {Superconductors with persistent zero-resistance currents serve as permanent magnets for high-field applications requiring a strong and stable magnetic field, such as magnetic resonance imaging. The recent global helium shortage has quickened research into high-temperature superconductors (HTSs)—materials that can be used without conventional liquid-helium cooling to 4.2 K. Herein, we demonstrate that 40-K-class metallic HTS magnesium diboride (MgB{sub 2}) makes an excellent permanent bulk magnet, maintaining 3 T at 20 K for 1 week with an extremely high stability (<0.1 ppm/h). The magnetic field trapped in this magnet is uniformly distributed, as for single-crystalline neodymium-iron-boron. Magnetic hysteresis loop of the MgB{sub 2} permanent bulk magnet was determined. Because MgB{sub 2} is a simple-binary-line compound that does not contain rare-earth metals, polycrystalline bulk material can be industrially fabricated at low cost and with high yield to serve as strong magnets that are compatible with conventional compact cryocoolers, making MgB{sub 2} bulks promising for the next generation of Tesla-class permanent-magnet applications.},
doi = {10.1063/1.4890724},
journal = {Applied Physics Letters},
number = 3,
volume = 105,
place = {United States},
year = 2014,
month = 7
}
  • Type-II and multiply connected type-I superconductors may experience magnetic forces that are significantly different from the well-known repulsive Meissner effect. In particular flux trapped by a superconductor may result in a force which has a stable position. We have calculated the magnetic force acting on a superconductor, based on a trapped flux model; the results have been compared with experiments at 4.2 K on (1) a block of Nb{sub 3}Sn (2), a disk of YBa{sub 2}Cu{sub 3}O{sub {ital x}}, and (3) a hollow cylinder of Pb. Most of the experimental results are in reasonably good agreement with the calculations. However,more » an interesting discrepancy exists in the frequency of small oscillations about the stable position.« less
  • In this paper we present calculations of levitation forces between a cylindrical permanent magnet and a cylindrical superconductor using a commercial finite element program. Force limits for zero field cooled and field cooled processes have been obtained using the Meissner effect and the perfect pinning hypothesis, respectively. Comparison of the experimentally determined forces with respect to these limits provides a simple estimation of the sample quality. The hysteretical behavior of the forces has been reproduced assuming a critical state model for the superconductor. Results are compared with experimental data. Excellent agreement has been found for forces measured after zero fieldmore » cooled process thus allowing us to estimate the critical current of the samples. As a further exploitation of the software capabilities we have investigated the effects of the superconducting sample geometry and the effects of different strategies of flux conditioning to optimize the levitation forces. {copyright} {ital 1997 American Institute of Physics.}« less
  • The vertical and horizontal forces and associated stiffnesses on a permanent magnet (PM) above a high-temperature superconductor (HTS) were measured during vertical and horizontal traverses in zero-field cooling (ZFC) and in field cooling (FC). In ZFC, the vertical stiffness was greater in the first descent than in the first ascent and second descent, and the stiffness in the second descent was between those of the first descent and the first ascent. At the FC position, the vertical stiffness was two times greater than the lateral stiffness at each height, to within 1{percent} of the vertical stiffness value. The cross stiffnessmore » of vertical force with respect to lateral position was positive for FC, but negative for ZFC. Free-spin-down experiments of a PM levitated above a HTS were also performed. These results showed that the coefficient of friction is double valued at frequencies just below the rotor resonance, a result attributed to cross stiffness in the PM/HTS interaction. A frozen-image model was used to calculate the vertical and horizontal forces and stiffnesses, and reasonable agreement with the data occurred for vertical or horizontal movements of the PM less than several mm from the FC position. {copyright} {ital 1999 American Institute of Physics.}« less
  • Structure and magnetic properties were studied for Tm{sub 2}(Co{sub 1-x}Fe{sub x}){sub 17} bulk nanocrystalline magnet synthesized by spark plasma sintering technique. X-ray diffraction results indicate both ingot and sintered magnet of Tm{sub 2}(Co{sub 0.7}Fe{sub 0.3}){sub 17} alloy exhibit hexagonal Th{sub 2}Ni{sub 17} type structure. The microstructure of the magnet is composed of Th{sub 2}Ni{sub 17} type nanograins with an average size of 35 nm detected by transmission electron microscopy and selected area electron diffraction patterns. Magnetic measurement shows that the remanence of the magnet is higher at 573 K than at 300 K, indicating there is a positive remanence temperaturemore » coefficient in the magnet. The anisotropy field of Tm{sub 2}(Co{sub 0.7}Fe{sub 0.3}){sub 17} alloy is 3.8 T, which is much higher than the H{sub A} of 2.3 T for the pure Tm{sub 2}Co{sub 17} alloy. The coercivity of the sintered magnet increases from 0.25 to 0.354 T after optimal annealing.« less