|
|
Research
Nugget 3: InSb-Quantum-Well/Metal Composites
 The
magnetoresistance (MR) of a material object contains a physical contribution
from the magnetic field dependence of the material parameters such as
the mobility or carrier concentration and a geometric contribution from
the dependence of the current path and output voltage on the sample shape
and electrode configuration. To date, only two classes of magnetic materials,
artificially layered metals which exhibit either giant MR (GMR) or tunneling
MR (TMR) and the manganite perovskites which exhibit colossal MR (CMR)
have been considered serious candidates in the effort to improve the room
temperature performance of MR sensors. For both of these classes, the
physical MR dominates. In contrast, our collaborators have found that
non-magnetic narrow-gap semiconductors containing patterned metallic inhomogeneities
(shunts), exhibit room-temperature geometric extraordinary MR (EMR) orders
of magnitude larger than the physical MR of other (magnetic) materials.
Since the sensitivity depends quadratically on mobility, materials with
high mobility are preferred for EMR sensors.
 Among
the numerous magnetic sensor applications that might beneficially employ
EMR materials, one of the most interesting is the read-head sensor for
high-density magnetic recording. This application requires sensor devices
of mesoscopic size with a semiconductor that has a thin conducting layer
close to the surface. The InSb quantum-well material grown at the Center
meets all the design requirements for read-write sensors. The development
of such sensors began 9 months ago as a collaborative effort between NEC
and the Center. The nanostructures are fabricated at NEC using electron
beam lithography and reactive ion etching. The room temperature EMR prepared
from an InSb quantum well of dimension 30 nm wide x 100 nm high x 3 mm
long is 4.75% at a relevant field of 0.05 T.
---S.A. Solin, D.R. Hines (NEC Research Institute)
J.S. Tsai, Yu. A. Pashkin (NEC Fundamental Research Laboratories)
S.J. Chung, N. Goel and M.B. Santos (CSPIN)
(submitted to IEEE Transactions on Magnetics)
|
