Physics Question #4497

Marty Ellis, a 39 year old male from Pittsburgh asks on December 27, 2008,

Can a sintered ore magnet be re-magnetized in a different configuration of its poles? Does it need be heated to its Curie point to be easily remagnetized differently?

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The answer

James Livingston answered on December 28, 2008

Yes, the poles of a magnet can be changed by exposing the magnet to a very high magnetic field in a new direction. Many of the best magnets are sintered--densified from powder by heating at high temperature, often under pressure. If the magnet is a neodymium magnet, at room temperature you will need a strong pulse magnetizer to provide enough field. However, if you heat the magnet significantly, even a modest magnetic field can magnetize the magnet in a new direction.

Some sintered magnets are "anisotropic" with a strongly favored axis of magnetization. Such magnets can be reversed with a sufficiently high reverse field (or a modest reverse field at high temperature) but cannot easily be magnetized in directions transverse to the preferred axis.

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