| 摘要 |
Magnetic recording media including permanent structures of aligned acicular particles have been proposed as a means of identifying and authenticating a medium. A structure which has an improved remanence difference signal is described. A method of making and examining such a structure is described. Arrangements of such media and record / read-out apparatus by which information can be recorded and read-out without interference from the structural remanence differences are described. The use of the media for security documents such as credit cards is described.
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