Philosophy & Scope

Materials for Spintronics
and Spin-resolved Transport

Prof. Kannan M. Krishnan (Principal Investigator)

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Spin Resolved Quantum Conductance in Nanowires
Funding: Campbell Endowment at UW

Project summary:

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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[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.

2003 Undergraduate Research Symposium Presentation

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