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Discussion in 'Electronic Basics' started by Chen, Jul 16, 2004.

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  1. Chen

    Chen Guest

    IBM-Stanford Spintronic Science and Applications Center

    What is spintronics?
    The word "spintronics" (short for "spin electronics") refers to devices
    that take advantage of electrons' quantum property called "spin." Electrons
    don't actually spin around an axis, although in many ways they may behave as
    if they do. More familiar is the electron's quantum property of "negative
    charge": Moving charge creates electrical current.

    Electron spin has two possible states, either "up" or "down." Aligning spins
    in a material creates magnetism. Moreover, magnetic fields affect the
    passage of "up" and "down" electrons differently. Under normal conditions,
    the spins of conducting electrons are roughly half-up and half-down.
    Controlling the spin of electrons within a device can produce surprising and
    substantial changes in its properties. A new generation of devices based
    upon the manipulation of spins in solids may have entirely new functionality
    that could provide a foundation for entirely new computational paradigms.

    For example, the first widely used spintronic device -- the Giant
    Magnetoresistive (GMR) spin-valve head for magnetic hard-disk drives --
    exhibits large changes in electrical resistance due to variations in the
    relative magnetic orientation of layers on either side of a spacer layer
    only 2-3 atoms thick. When the orientations are in the same direction
    ("parallel"), electrons with one type of spin pass freely while those with
    the opposite spin meet greater resistance. When the magnetic orientations
    are in opposite directions ("antiparallel"), all the electrons meet
    resistance, resulting in a high overall electrical resistance through the
    head. By designing the structure so a faint external magnetic field would
    change the relative magnetic orientations of the key layers, the GMR head
    became an extraordinarily sensitive magnetic-field sensor. Pioneered by IBM
    in 1997, the GMR head enabled hard-disk drives to read smaller data bits,
    which led to a more than 40-fold increase in data-storage density over the
    past seven years.

    Spintronic structures are also at the heart of Magnetic Random Access Memory
    (MRAM), a fast non-volatile memory concept originally proposed by IBM and
    currently being developed by IBM, Infineon and others.
  2. KevinR

    KevinR Guest

    And . . . ?
  3. Sporkman

    Sporkman Guest

    It's a topic!
    Are you contributing?
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