Patent ID: 7977111

Claim:
A magnetic sensor for the identification of a chemical or biological species to which are bonded small magnetized particles, by means of a characteristic signature produced by said magnetized particles, comprising: a substrate having a planar surface on which is formed a plurality of species binding sites; a regular array of MTJ cells formed below said substrate surface, wherein each MTJ cell includes a planar free layer having an easy axis, a hard axis and a threshold switching field and wherein said free layer plane is parallel to said substrate plane; an MTJ cell selection and resistance measuring circuit for addressing each said MTJ cell in said array and determining variations in the resistance of each said cell and generating a signal indicating said variations; a signal analysis algorithm for identifying a particular correlation between cell resistance variations among two or more substantially neighboring MTJ cells in said regular array, wherein said resistance variations have been determined through the application of said cell selection and resistance measuring circuit; wherein, said particular correlation is generated by the presence of two clusters of MTJ resistance variations of approximately equal amplitude but of opposite sign and wherein said clusters are laterally disposed about a vertical axis aligned along said hard axis of an MTJ cell in said array; and wherein said correlation is the signature of a magnetic particle that is magnetized by an externally imposed magnetic field and whereby the presence of said signature is indicative of the presence of a species bonded to said surface, on which species said magnetized particle is bonded.