The purpose of this investigation
is to find materials that exhibit 100% spin polarized
electrical currents in nanowires, or spin-resolved
quantum conduction. In the limit of decreasing nanowire
size, the conductance is determined by the number
of transmission channels available - each with a
value of Go = e2/h -1. These transmission channels
are analogous to energy states at the Fermi level,
therefore in spin degenerate materials, the observed
conduction becomes G = 2e2/h. There is controversy
surrounding the expected conductance in ferromagnetic
materials. Although the majority spin is at slightly
lower energy than the minority spin, transmission
channels associated with each spin may still be
available for conduction. Halt metallic systems
are anticipated to exhibit spin-resolved quantum
conduction. These materials have no minority spin
transmission channels at the Fermi level. [1]
Atomically small point contacts are created using
the mechanically controlled break junction technique
[2]. Contacts of this nature occur when two macroscopic
objects, usually wires, are brought into contact
and separated. A neck of atomics will form between
the macroscopic wires, and its dimensions will reach
atomic size at the last stages of separation. A
fast oscilloscope along with a current to voltage
converter and an amplifier are employed to determine
the conductance of the evolving point contact.
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References:
[1] Warren Pickett and Jagadeesh Moodera, Physics
Today June 1999, page 33.
[2] J.L. Costa-Kramer, N. Garcia, P. Garcia-Mochales,
P.A. Serena. Surface Science Letters 342 (1995)
L1144
For additional information email Zach Lingley
at zrl@u.washington.edu.
