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update.281 (fwd)
Hi all,
Forwarded message:
> Date: Mon, 29 Jul 96 10:18:54 EDT
> From: [email protected] (AIP listserver)
> Subject: update.281
>
> PHYSICS NEWS UPDATE
> The American Institute of Physics Bulletin of Physics News
> Number 281 July 29, 1996 by Phillip F. Schewe and Ben Stein
>
> SOLAR NEUTRINO FLUX IS NOT CORRELATED WITH
> SUNSPOT ACTIVITY. The Kamiokande detector, situated a
>
> THE PHYSICS OLYMPIAD IN OSLO, like the sports Olympiad
>
> TUNNEL JUNCTION MAGNETORESISTANCE may lead to
> higher-density magnetic storage devices. Physicists have known for
> some time that sandwiches of alternating magnetic and nonmagnetic
> microlayers can undergo a change in electrical resistance in the
> presence of an external magnetic field (arising, say, from a tiny
> domain on a segment of magnetic tape). This magnetoresistance
> (MR) effect can be used to decode binary data and has been
> employed in reading heads in computer hard drives. Giant
> magnetoresistance (GMR), a stronger version of MR, affords even
> greater data-decoding sensitivity. Prototype hard-drives with read
> heads using GMR have achieved areal data densities of 3
> Gbits/sq.in. Tunnel junction magnetoresistance (JMR) is yet another
> approach to transforming a tiny magnetic field into a change in
> resistance. Unlike the all-metal GMR sensor, a room-temperature
> JMR sensor consists of two metal (ferromagnetic) layers separated
> by an insulating layer. A JMR trilayer junction tested recently at
> MIT is only 20 nm thick and the signal (the fractional change in
> resistance) was 23%, compared to a signal of less than 7% for a
> 40-nm-thick, 4-layer GMR prototype. MIT physicist Jagadeesh
> Moodera ([email protected]; 617-253-5423) suggests that
> the more compact size, relatively larger signal, and the low sub-nanoamp operating current of the JMR sensor could make for easier
> engineering of devices and lower production costs. An areal density
> of more than 10 Gbits/sq.in. is possible, he says. (J.S. Moodera et
> al., Applied Physics Letters, 29 July.)
>