Patent ID: 7729093
Filing Date: 2010-06-01
Classification: G01N,G01R

Abstract:
1. A method to detect the presence of a magnetic bead, comprising: providing a detector that signals the presence of a magnetic field through a change in its electrical resistance, said detector having an upper surface that is parallel to a free layer of the detector; causing said free layer to be magnetized in a bias direction; attaching said magnetic bead to said upper surface at a binding site; providing a static magnetic field, having a value, in a direction normal to said upper surface; providing an alternating magnetic field having a frequency, a first amplitude, and a direction parallel to said upper surface; and varying said frequency and said static field value until ferromagnetic resonance (FMR) occurs, whereby said magnetic bead emits a magnetic field that rotates at said FMR frequency at a second amplitude, thereby causing said detector signal to peak and to signal the presence of said magnetic bead.