Devices using addressable magnetic tunnel junction array to detect magnetic particles
US7977111B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jan 18, 2008 |
| Grant date | Jul 12, 2011 |
| Priority date | — |
| Expiry date | Jul 31, 2029 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S436/806
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A magnetic sensor for identifying small superparamagnetic particles bonded to a substrate contains a regular orthogonal array of MTJ cells formed beneath that substrate. A magnetic field imposed on the particle, perpendicular to the substrate, induces a magnetic field that has a component within the MTJ cells that is along the plane of the MTJ free layer. If that free layer has a low switching threshold, the induced field of the particle will create resistance changes in a group of MTJ cells that lie beneath it. These resistance changes will be distributed in a characteristic formation or signature that will indicate the presence of the particle. If the particle's field is insufficient to produce the free layer switching, then a biasing field can be added in the direction of the hard axis and the combination of this field and the induced field allows the presence of the particle to be determined.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.