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

issues and need to be overcome.
Two various approaches, based on various magnetic phenomena, are being pursued. The first, being investigated by Gary Prinz
and his colleagues at the Naval Research Laboratory (NRL) in Washington, D.C., exploits the fact that the electrical resistance of
a few materials modifications in the presence of a magnetic field-a phenomenon known as magneto-resistance. For a few multi-layered
materials this effect is particularly powerful and is, accordingly, called "giant" magneto-resistance (GMR). Since 1997, the exploitation
of GMR has made cheap multi-gigabyte hard disks commonplace. The magnetic orientations of the magnetised spots on the surface
of a spinning disk are detected by measuring the modifications they induce in the resistance of a tiny sensor. This technique is so sensitive
that it means the spots can be made smaller and packed closer together than was previously possible, thus increasing the capacity
and reducing the size and cost of a disk drive.
Dr. Prinz and his colleagues are now exploiting the identical phenomenon on the surface of memory chips, rather than spinning disks. In
a conventional memory chip, every binary digit (bit) of data is represented using a capacitor-reservoir of electrical charge that is
either empty or full-to represent a zero or a one. In the NRL's magnetic design, by contrast, every bit is stored in a magnetic element
in the form of a vertical pillar of magnetisable material. A matrix of wires passing above and beneath the elements allows every to be
magnetised, either clockwise or anti-clockwise, to represent zero or one. a different set of wires allows current to pass through any
particular element. By measuring an element's resistance you can determine its magnetic orientation, and hence whether it is storing
a zero or a one. Since the elements retain their magnetic orientation even when the power is off, the outcome is non-volatile memory.
Unlike the elements of an electronic memory, a magnetic memory's elements are not easily disrupted by radiation. And compared with
electronic memories, whose capacitors need constant topping up, magnetic memories are simpler and consume less power. The NRL
researchers plan to commercialise their device through a company called Non-Volatile Electronics, which recently began work on the
necessary processing and fabrication techniques. But it will be a few years before the 1st chips roll off the production line.
Most attention in the field is focused on an option approach based on magnetic tunnel-junctions (MTJs), which are being

Earning:   Approval pending.