Ben James
L01 – Whit Smith
Team MagLev
Technical Review: Magnets – Rare Earth Magnets & Magnetic Levitation
Introduction
Magnetism and electromagnetism are concepts currently used in a wide range of
applications from medical to military, from sensors to saving data, and from sound to visual.
Magnetisms mechanical force without physical medium is the unique factor that sets it apart
from other forms of mechanical force while its scalability allows it to be used on designs from
the nanometer to the megameter level. Electromagnetism has the same ability of mechanical
force without physical medium yet can be turned off, reverse its force, and vary the amount of
force applied through electric current. Though breakthroughs in the area of magnetism have not
been many in the last decade the uses of magnets have spread widely, become more complex,
and the cost has come down. Rare earth magnets are a category of magnets which have a more
powerful magnetic field and are needed in specific applications such as levitation. This paper
briefly examines some commercial applications of rare earth magnets and magnetic levitation
and summarizes the state of the technology.
Commercial Applications of Rare Earth Magnets & Magnetic Levitation
Civilian
The largest use of rare earth magnets in civilian use is currently in consumer electronics.
Speakers, computer hard drives, and laptop sensors all use neodymium magnets. In addition
some rare earth magnets are used for “frictionless” bearings in motors, fans, or generators. These
have significantly less friction but due to the fluid friction of their environment they cannot truly
be called frictionless.
In terms of magnetic levitation the most notable application of rare earth magnets for
consumers are in novelty items such as a floating picture frame or science projects for children
though safety standards are becoming stricter for many magnetic toys [1]. Other civilian uses of
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these magnets for levitation include maglev trains which have projects in Germany, the United
States, Japan, and India among other countries. Neodymium magnets are also used in these
applications as the other major rare earth magnet, samarium-cobalt, has a magnetic field 42% of
that of neodymium. In comparison alnico magnets which were the standard before rare earth
magnets have a magnetic field 23% of that of neodymium [2]. Research for implementation of
maglev trains on a massive scale is being conducted throughout the world depending on the
companies seeking profit or which governments are investing in the technology. In the United
States one of the most developed projects to date is a test track located in Powder Springs, GA
and is being run by American Maglev Technology [3].
Neodymium magnets on a small scale can be affordable for the average consumer at
$0.11- $0.60 per magnet [4].
Military
The closest related military application of rare earth magnets and levitation is electric gun
or what is commonly known as a railgun. The railgun uses electrically charged rails to create a
strong magnetic field which propels a projectile down the rails. This method has been used to
achieve acceleration of a projectile with 10.6 MJ of energy to a velocity seven times the speed of
sound [5]. The project has spent millions of dollars on development thus far and though the
research is not directly related to levitation it shows the relative power of electromagnetic
systems.
Research
Florida State University’s National High Magnetic Field Laboratory boasts the world’s
highest magnetic field for a continuous field magnet at 45 T [6] by combining a superconducting
magnet and a resistive magnet. For comparison the Earth’s magnetic field is about 0.00005 T [7].
Technology of Rare Earth Magnets & Levitation
Operation
Levitation is achieved in a number of ways ranging from permanent rare earth magnets
and graphite to complex electromagnetic systems yet always contain rare earth magnets. The
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challenge of magnetic levitation is not in raising the object but controlling it once it has levitated.
This is achieved typically by surrounding the objects with an electromagnetic structure on its
sides and using a controls system to monitor and adjust the position of the levitated object.
Implementation
Depending on the application levitation can be achieved simply and affordably with
online kits like those found at [8] for $29.99 or expensively as with maglev trains.
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[1] U.S. Consumer Product Safety Commission. Office of Information and Public Affairs.
"Small Magnets Are Injuring Children; CPSC Releases Stronger Warning to Parents."
Press release. NEWS from CPSC. 19 Apr. 2007. Consumer Product Safety Commission.
21 Jan. 2009 <http://www.cpsc.gov/cpscpub/prerel/prhtml07/07163.html>.
[2] Furlani, Edward P. Permanent Magnet and Electromechanical Devices : Materials, Analysis,
and Applications. New York: Academic Press, 2001, pp. 55-56.
[3] "AMT - Mass Transit For The Future - About Us." AMT. 2005. American Maglev
Technology. 21 Jan. 2009 <http://americanmaglev.com/index.php?option=com_content&task=view&id=5&Itemid=26#solution>.
[4] "Forcefield - Otherpower - Wondermagnet Online Store." Magnet Products. Force Field
Magnets. 21 Jan. 2009
<http://www.forcefieldmagnets.com/catalog/index.php?cPath=23_37>.
[5] "Technology Review: Electromagnetic Railgun Blasts Off." Technology Review: The
Authority on the Future of Technology. 06 Feb. 2008. MIT. 21 Jan. 2009
<http://www.technologyreview.com/Infotech/20164/?nlid=857&a=f>.
[6] "Meet the Magnets: 45 Tesla Hybrid." National High Magnetic Field Laboratory. Florida
State University. 21 Jan. 2009
<http://www.magnet.fsu.edu/mediacenter/features/meetthemagnets/hybrid.html>.
[7] "An Introduction to Magnets (full article)." National High Magnetic Field Laboratory.
Florida State University. 21 Jan. 2009
<http://www.magnet.fsu.edu/education/tutorials/magnetacademy/magnets/fullarticle.html
>.
[8] "ThinkGeek :: Levitron - Anti-Gravity Top." ThinkGeek :: Stuff for Smart Masses. 21 Jan.
2009 <http://www.thinkgeek.com/geektoys/cubegoodies/5bb6/>.
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