![]() ![]() H max of neodymium magnets is about 18 times greater than "ordinary" magnets by volume.H max is proportional to J s 2, so these materials have the potential for storing large amounts of magnetic energy.This gives the materials high remanence ( saturation magnetization J s ). In a magnet it is the unpaired electrons, aligned so they spin in the same direction, which generate the magnetic field. This is a consequence of incomplete filling of the f-shell, which can contain up to 7 unpaired electrons. Their orbital electron structures contain many unpaired electrons in other elements, almost all of the electrons exist in pairs with opposite spins, so their magnetic fields cancel out, but in rare-earths there is much less magnetic cancellation. Second, atoms of rare-earth elements can have high magnetic moments. ![]() The resistance of the crystal lattice to turning its direction of magnetization gives these compounds a very high magnetic coercivity (resistance to being demagnetized), so that the strong demagnetizing field within the finished magnet does not reduce the material's magnetization. Like other magnets, rare-earth magnets are composed of microcrystalline grains, which are aligned in a powerful magnetic field during manufacture, so their magnetic axes all point in the same direction. This means that a crystal of the material preferentially magnetizes along a specific crystal axis but is very difficult to magnetize in other directions.
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