Indian Institue of Management 2000 M.B.A CAT - Question Paper

investigated by researchers at chip makers such as IBM, Motorola, Siemens and Hewlett-Packard. IBM's research team, led by Stuart
Parkin, has already created a 500-element working prototype that operates at 20 times the speed of conventional memory chips and
consumes one % of the power. every element consists of a sandwich of 2 layers of magnetisable material separated by a barrier of
aluminium oxide just 4 or 5 atoms thick. The polarisation of lower magnetisable layer is fixed in 1 direction, but that of the
upper layer can be set (again, by passing a current through a matrix of control wires) either to the left or to the right, to store a zero
or a one. The polarisations of the 2 layers are then in either the identical or opposite directions.
Although the aluminium-oxide barrier is an electrical insulator, it is so thin that electrons are able to jump across it via a quantummechanical
effect called tunnelling. It turns out that such tunnelling is easier when the 2 magnetic layers are polarised in the identical
direction than when they are polarised in opposite directions. So, by measuring the current that flows through the sandwich, it is
possible to determine the alignment of the topmost layer, and hence whether it is storing a zero or a one.
To build a full-scale memory chip based on MTJs is, however, no easy matter. According to Paulo Freitas, an expert on chip
manufacturing at the tech. University of Lisbon, magnetic memory elements will have to become far smaller and more reliable
than current prototypes if they are to compete with electronic memory. At the identical time, they will have to be sensitive enough to
respond when the improper wires in the control matrix are switched on, but not so sensitive that they respond when a neighbouring
element is changed. Despite these difficulties, the general consensus is that MTJs are the more promising ideas. Dr. Parkin says his
group evaluated the GMR approach and decided not to pursue it, despite the fact that IBM pioneered GMR in hard disks. Dr. Prinz,
however, contends that his plan will eventually offer higher storage densities and lower production costs.
Not content with shaking up the multi-billion-dollar market for computer memory, a few researchers have even more ambitious plans
for magnetic computing. In a paper published last month in Science, Russell Cowburn and Mark Welland at Cambridge University
outlined research that could form the basis of a magnetic microprocessor- a chip capable of manipulating (rather than merely storing)

Earning:   Approval pending.