"Faster, better, smaller, cheaper." This is the battle cry of computer advancement. But is there no limit? Often I find myself wondering what the next step will be. After all, how minuscule can computers and computer components, which hold so much, be. Well apparently the computer industry is not done just yet. Giant Magnetoresistance, the GMR effect, is the next technological advancement to be explored.

The GMR effect is used to sense magnetic fields of data in hard disk drives. Originally, IBM used magnetoresistive read heads to read the magnetic fields of data from the hard disk. In 1991, though, IBM researchers together with the Computational Center for Industrial Innovation (CCII) and ORNL scientists introduced spin valves, (composed of a Co_90Fe_10/Cu material for all you chemistry buffs out there), a GMR structure which responds to very small magnetic fields produced by written data in a hard disk drive. Using the regular magnetoresistive read heads, IBM demonstrated a possible density of three gigabits per square inch in 1994 and five gigabits per square inch in 1996. With the use of the GMR effect, though, IBM announced that a density of 11.6 gigabits per square inch is under investigation.

When magnetic fields are applied to magnetic materials, electrical resistivity is reduced. The MR and GMR read heads sense the change in electrical resistance in the magnetic disk created by the magnetic fields in which data is written to the disk. The sensor's output voltage is the product of this resistance change. The signal is then amplified and sent to the hard disk drive's data detection electronics. The GMR head is more sensitive than the regular MR head in that the GMR head detects electronic resistance in two ways rather than one. The GMR head uses the quantum nature of electrons which has two electron spin directions. The electrons which spin in a direction parallel to the material's magnetic orientation produce low resistance, while the electrons which spin in a direction perpendicular to the material's magnetic orientation produce a higher resistance. The quantum nature of electrons, therefore, creates a greater sensitivity to changes in electronic resistance. This, in turn, allows more data storage in a smaller area.

As areal densities continue to grow well past ten gigabits per square inch, an even more advanced technology, beyond that of the GMR effect, may be needed. But for now this Giant MR effect, indeed a giant step in computer technology, helps continue the quest for, "Faster, better, smaller, cheaper."