ECE5320 Assignment#1 by JR4C1E

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									              ECE5320 Mechatronics
Assignment#01: Literature Survey on Sensors and Actuators

          Topic: Magneto resistive sensors


           Prepared by: Shashidhar Reddy .Y

     Dept. of Electrical and Computer Engineering
                  Utah State University
    E: ; T: (435)797-; F: (435)797-3054 (ECE Dept.)
                        W: http://
                        3/10/2006
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      Conventional Vs Magnetic sensing




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            MAJOR APPLICATIONS




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     MAGNETIC SENSOR APPLICATIONS




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            BASIC WORKING
                  OF
              MR SENSORS




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            Anisotropic magnetoresistive (AMR)
                          sensor

                       Magnetization M
                                                              R=R┴+ΔRAMRcos2 θ
                  θ
                             Current I



            The theory of the AMR sensor is based on the complex
            ferromagnetic process in a thin film
            Magnetoresistance variation with angle between M and I
            AMR ratio for typical ferromagnetic materials at room
            temperature is around 1-3%
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             Obtaining parallel, antiparallel magnetic
                           alignment
     • pinned sandwiches
            – Consist of two magnetic layers, soft layer and hard layer
     • Anti ferromagnetic multilayer
            – Consist of multiple repetitions of alternating magnetic and
              nonmagnetic layers
            – The polarized conduction electrons cause antiferromagnetic
              coupling between magnetic layers
     • Spin valves
            – An additional layer of an antiferromagnetic material is
              provided on the top or bottom
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    Giant magnetoresistive (GMR) sensor




        Two different ferromagnetic materials sandwiched by a thin
        conduction layer
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            Antiferromagnetic multilayers




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 Use of GMR in hard drive read head




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            FEATURES OF A GMR
  • The key structure in GMR materials is a spacer
    layer of a non-magnetic metal between two
    magnetic metals .
  • The overall resistance is relatively low when the
    layers were in parallel alignment and relatively
    high when in anti-parallel alignment. For his
    pioneering work in GMR, Parkin won the
    European Physical Society's prestigious 1997
    Hewlett-Packard Europhysics Prize along with
    Gruenberg and Fert.
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            WORKING OF AN MR HEAD
                 Basic hard Disk set up




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            HARD DISK HEAD SETUP




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             MR SENSOR AS HEAD


    MR
    HEAD
                                                                             BIT ON
                                                                             HDD

MAGNITUDE
OF                                                                             CHANGE IN
RESISTANCE                                                                     RESISTANCE
CHANGE




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              GMR SENSOR AS A HEAD
            (More sensitive than an MR head)



LAYERS OF
GMR                                                                              HIGHER
SENSOR                                                                           RESISTANCE
                                                                                 CHANGE IN A
                                                                                 GMR




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     Decrease in GMR resistance as the bit passes beneath




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            Medium Resistance




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                High Resistance




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            ADVANTAGES OF A GMR

     The increased signal offered in the GMR allows
     more information to be stored on a hard disk.
     This translates into very large capacity hard
     drives that can be made cheaper and more
     reliable.




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            Parameters for GMR sensor
  • Magnetic layers: 4~6 nm
  • Conductor layer 3~5 nm in sandwich structure
       – This thickness is critical in antiferromagnetic
         multilayer GMR sensors, typically 1.5~2 nm
  • Switching field 3~4 KA/m (35~50 Oe) for
    sandwich structure and 250 for multilayer
    structures



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                  REFERENCE
  • http://www.stoner.leeds.ac.uk/research/gmr.htm
  • http://www.ornl.gov/info/ornlreview/v30n3-
    4/giant.htm
  • http://www.pcguide.com/ref/hdd/
  • http://www.howstuffworks.com/hard-disk.htm
  • http://www.st-
    andrews.ac.uk/~www_pa/Scots_Guide/info/comp
    /conduct/conduct/conduct.htm

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               To explore further
  • http://www.research.ibm.com/research/gmr.html
  • http://www.research.ibm.com/research/demos/gm
    r/cyberdemo3.htm
  • http://mrsec.wisc.edu/Edetc/cineplex/GMR/index.
    html




9/13/2012     ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

								
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