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GMR Sensors Sensors, Instrumentation, and Measurements in Electronic Applications EE 87022

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GMR Sensors Sensors, Instrumentation, and Measurements in Electronic Applications EE 87022

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    1. GMR Sensors Sensors, Instrumentation, and Measurements in Electronic Applications EE 87022 Hubert George

    3. GMR Sensors Stands for Giant magnetoresistance (GMR) sensors and can achieve a change of resistance of 10%20% It is based on thin-film magnetic technology In contrast with conventional magnetoresistance (MR), which exhibit a change of resistance of <3%

    4. GMR

    5. GMR GMR are films which have two or more magnetic layers separated by a nonmagnetic layer. The GMR effect manifests itself as a significant decrease in electrical resistance in the presence of a magnetic field. No magnetic field: The direction of magnetization of adjacent ferromagnetic layers is ant parallel. High-resistance magnetic scattering. Magnetic field is applied, the magnetization of the adjacent ferromagnetic layers is parallel. Lower resistance.

    6. GMR Types of GMR: Multilayer GMR: Very thin (about 1 nm) non-ferromagnetic spacer. RKKY coupling (Ruderman-Kittel-Kasuya-Yosida) Spin valve GMR: (~3 nm) non-ferromagnetic spacer, no RKKY coupling. Granular GMR: Solid precipitates of a magnetic material in a non-magnetic matrix. Only seen in matrices of copper containing cobalt granules

    7. GMR application

    8. GMR application - HD

    11. GMR sensors use the quantum nature of electrons (two spin directions, up and down): Conduction electrons with a spin direction parallel to a material's magnetic orientation move freely, producing low resistance. Conduction electrons with spin direction opposite to the material's magnetic orientation are hampered by more frequent collisions with atoms in the material, producing higher resistance.

    12. GMR Mechanism

    13. Full sensitivity can be achieved by either changing the slope of this response curve or by adjusting the amplitude of the transverse magnetic field: Changing the thickness of the sensing layer Reducing the magnetic field from the disk.

    14. Thanks. Any Question? Youtube HD video

    15. Ref. Robert W. Schneider, Carl H. Smith. Low Magnetic Field Sensing with GMR Sensors. Part I: The Theory of Solid-State Magnetic Sensing. Nonvolatile Electronics, Inc. Sensors, Sep 1, 1999. Jim Belleson, Ed Grochowski. The era of giant magnetoresistive heads. http://www.hitachigst.com/hdd/technolo/gmr/gmr.htm#5 Wikipedia. http://en.wikipedia.org/wiki/Giant_magnetoresistance http://www.research.ibm.com/research/gmr.html http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=00723205

    16. Ferromag Antiferromag Diamag Paramag

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