The 2007 Nobel Prize in Physics has gone to physicists who discovered the GMR effect. Read all about it at the Nobel website. GMR or Giant magneto resistance is the large change of resistance of special materials when put into a magnetic field. GMR is used in the read heads of hard drives on our computers. A “read head” reads the data stored on the hard drive (writing is done by a separate head).
Data on a hard drive is stored in binary (1’s and 0’s). A small north pole on the disk surface may represent ‘1′ and a south pole ‘0′). If your hard disk has a capacity of 1 GB, for example, then your hard disk will have 8 billion such little magnets on the hard drive (1 GB = 1 billion bytes, 1 byte = 8 bits = 8 magnets. Therefore 1 GB=8 billion magnets). When a read head passes over a bit (which is a small magnet) the resistance of the read head changes (the small magnet has its own magnetic field. The read head is made up of GMR material which changes resistance when exposed to magnetic field of the bit). The resistance will be different if it a North Pole (1) or a South Pole (0). A constant voltage is applied across the read head. The voltage causes a current to flow within the hard drive read head. As the resistance changes, depending on whether the bits are 1 or 0, the current also changes. So, by scanning across a particular part of the hard drive (where your mp3 might be stored) and see the change in current, the stream of 1s and 0s that represent your mp3 can be deciphered.
For all those budding physicists out there, there is an extremely simple and amazing article on GMR on the Nobel website. It explains the diagram above! I’ve just finished reading it and it must be one of the best explanatory articles on science I’ve ever read! Read it if you are interested in Solid State Physics. It will strengthen your fundamentals in less than an hour. Only simple equations have been used! Tip Read the introductory press releases on the Nobel website before you leap into the article mentioned above.
Also you might want to see some really cool animations on GMR at the IBM website.
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