Rare-earth permanent magnets are ideally suited to generate magnetic fields comparable to their spontaneous
polarization JS: Near-square hysteresis loops and large values of the coercivity and anisotropy fields greatly simplify
magnet design, as each magnet block is effectively transparent to the magnetic fields produced elsewhere in the magnet
assembly. The fields generated by compact and efficient magnet structures requiring no continuous expenditure of
energy can be static or variable, uniform or nonuniform. Permanent magnets are fully competitive with electromagnets
for fields up to 2T, and fields as high as to 5 T can be produced in a small volume. When a field with a rapid spatial
variation is required, permanent magnets may offer the only practicable solution. Both permanent magnet structures
and the uses to which they are put are reviewed, classifying the magnet applications in terms of the nature of the field,
the effect on the magnet and the physical effect exploited.