Patent ID: 7950587

Claim:
A data-storage device, comprising: a medium having a surface; and a plurality of data-containing loci arranged on the surface, each locus having a respective amount of magnetically responsive particles, the respective amounts being selected from a range of amounts and being different in at least some of the loci, wherein the respective amount at a particular locus corresponds, at least in part, to a respective unit of data stored by the locus, wherein the magnetically responsive particles in each locus are of a respective type selected from a range of multiple selectable types, such that at least some of the loci have different types; the selectable types differ from each other by at least one characteristic selected from the group consisting of material type, particle size, particle shape, particle density, and particle distribution; and the selected type at a particular locus corresponds, at least in part, to the respective unit of data stored by the locus.