Polymodal magnetic recording media and compositions useful therein

Abstract

Polymodal magnetic information-recording articles formed with at least two different populations of magnetic powders, whereby at least one of the powders, being of lower intrinsic coercivity and forming means to accept a noise interference pattern, accepts a pattern which serves as a means to verify the authenticity of, or means to detect previous tampering with, the magnetic recording device. More generally, the disclosure relates to polymodal recording media characterized by incorporation of a plurality of independently-erasable ferromagnetic powder populations and processes for making and using said media. Particular advantage is disclosed for such media having a relatively small ratio of coercivity between easier and harder axis and for material wherein shape anisotropy is absent from adjacent modes in a polymodal system.