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Hard Disks to Pass 1Tbit per Square Inch
By Steve Bush -- Electronics Weekly, 8/16/2006
Hard disk drives could be dramatically enhanced with storage densities beyond one terabit per square inch as a result of magnetic sensor research being carried out at the Hitachi Cambridge Laboratory in partnership with the Universities of Cambridge and Nottingham.
The key step is that researchers in Cambridge and Nottingham along with the Czech Institute of Physics have produced a magnetic sensor based on a new effect called Coulomb blockade anisotropic magnetoresistance (CBAMR).
“It is a device which has a very high resistance change in magnetic fields which will make it very good for hard disk read heads,” Senior Hitachi Researcher Dr. David Williams told Electronics Weekly.
Current-generation GMR and next-generation TMR (giant and tunneling magnetoresistive) hard disk heads will cease to work if disk track width are cut much from the current 100nm because they rely on ferromagnetism. “When you make things of the order of 10mm to 20nm, you hit the super paramagnetic limit and you can’t maintain ferromagnetic orientation. Even before you get that small, you get fluctuations that lead to magnetic noise,” said Williams.
CBAMR devices are made from semiconductors so no internal field is required for operation, said Williams.
The sensor is in the form of a single electron transistor and is a thin film of GaMnAs which shows a 1000:1 resistance swing in response to magnetic field changes, although this is at cryogenic temperatures.
“Although this first CBAMR-device works only at low temperatures the research team has shown that CBAMR is a generic effect which persists to high temperatures in devices made from metal ferromagnets with strong spin-orbit coupling,” said Hitachi, although it did not say if high-temperature devices could be made as small.
Hitachi also announced the development of the first silicon-technology embodiment of extraordinary magnetoresistance.
Electronics Weekly is the London-based sister publication of Electronic News.
