Localized Field Permanent Magnet Arrays

Very short bar magnets can be grouped into linear arrays in such a way as to give a more localized field than does a single magnet of about the same size. Shaping the field from small magnet arrays is particularly important in the design of permanent magnet memories where the information is stored by the presence or absence of permanent magnets. To achieve high information density it is necessary to design magnet structures with very localized fields. Measurements of the response of a memory sensing element as a function of its distance from various magnets show that a linear array has a much stronger effect when very close to the sensor than does a single magnet of similar size and dipole moment.