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Strongest permanent magnets
Strongest permanent magnets: Sm2Co17 and Nd2Fe14B
Strongest permanent magnets
Modern permanent magnets are made of special alloys to create increasingly better magnets. The most common families of magnet materials today are: Ferrites; Alnicos (Aluminum-Nickel-Cobalt); Ceramics; Samarium-Cobalts; and Neodymiums (Neodymium-Iron-Boron, NdFeB). Neodymiums and Samarium-Cobalts are collectively known as Rare Earths.
Modern magnet materials are made through casting, pressing and sintering, compression bonding, injection molding, extruding, or calendaring processes.
The most powerful permanent magnets available today are the Rare Earths. Of the Rare Earths, Neodymium-Iron-Boron types are the strongest. However, at elevated temperatures (of approximately 150 C and above), the Samarium Cobalt types can be stronger that the Neodymium-Iron-Boron types (depending on the magnetic circuit).
New world record: Strongest permanent magnets made in Dresden
Scientists from the Institute for Solid State and Materials Research Dresden (IFW) made a permanent magnet of supercondacting materials which trapped a permanent magnetic field of 14,35 Tesla at a temperature of 22.5 Kelvin. With this result Dresdenīs researchers considerably exceed their own world record set in June this year, and extend the leading position in the world wide competition for higher field strengths in permanent magnets.
Dresden 1999-10-25
Permanent magnets are widely used in devices as common as catches and bicycle dynamos as well as in motors and computers. Usually they consist of materials containing iron and cobalt. The field strength at the surface of a customary magnet hardly exceeds 1 Tesla. Recently, much stronger permanent magnets can be made of superconducting materials on the condition that the material is cooled down to the critical temperature of about 90 Kelvin. The world wide competition for higher field strengths in permanent magnets arrived at 10.1 Tesla in 1996. This record set by the Houston University, Texas, was unchallenged up to June 1999 when the Solid State and Materials Research Dresden (IFW) has achieved 11,4 Tesla. To illustrate the levitation force of such a field one can say that two of those magnets effect on each other with a force of 500 kilogram per square centimetre. Now Dresdenīs materials scientists could shift the record once more up to considerably higher field strengths. 14,4 Tesla is the new record value achieved at October 15, 1999 in the IFW with superconducting magnets at 22.5 Kelvin. Superconducting magnets are effected by enormous radial tractive forces that are able to tear up the magnet itself. That's why this strong superconducting magnet needs to be bandaged up by a steel mantle although the mechanical strength of the superconductor was additionally increased by silver additives. Nevertheless the mechanical forces remain the limiting factor for the further enhancement of magnetic fields trapped in superconducters. Concerning the materials development there is the potential to achieve even higher magnetic field strengths. The superconducting bulk material (Yttrium-Barium-Copper-Oxygen) is prepared in the IFW by a modified melt process using seed crystals for texturing. Further improvement of superconducting properties could be reached by special material's treatment as well as by tin additives. Magnetic field strengths of 14 Tesla and above can of course be generated by copper coils. But this requires a large amount of energy of about 10 Megawatt involved. For certain applications like magnetic bearings and motors the use of superconducting magnets represents solutions more elegant and in the long run less expensive.
The IFW Dresden is devoted to fundamental and applied research and development, with particular emphasis on the fields of solid state and materials research. The research programme is focused on functional materials, both in bulk and thin films. In an interdisciplinary approach it combines fundamental research in physics, chemistry and material science with the specific needs of technological application. The IFW Dresden is funded to equally by the Federal Republic of Germany and the Free State of Saxony. The Institute has presently about 400 staff members, including about 70 PhD students and about 20 trainees.
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