Spin-Precession Organic Magnetic Sensor

Abstract

This report consists of two parts--results from La0.7Sr0..3MnO3 (LSMO) studies carried out in collaboration with the University of Delaware (UD) and the University of California at Riverside (UCR); and results from CoFe50Al25Si25 (CFAS) studies carried out in collaboration with Arizona State University (ASU)--both conducted under ONR Contract (N00014-09-C- 0292). The objective of the project is to develop an ultrasensitive magnetic sensor for room temperature operation. The requirements are (a) half-metallic ferromagnetic contacts with high Curie temperature, Tc and (b) polymer with very long spin lifetimes. Previously under this program we demonstrated (a) growth of high-quality LSMO with critical temperature Tc ~360 K and metal-semiconductor transition temperature, TMS > 400 K; (b) charge and spin injection from LSMO into low-mobility polymers; and (c) high magnetoresistance (MR) in micron-thick polymer devices. The results of this study were published in Applied Physics Letters. In the first part of this year (June 2010 to September 2010), we fabricated several devices with LSMO and polymer (P3HT) and evaluated the magnetic sensor operation. While spin precession, a requirement for ultra-high sensitivity, could be observed at low temperature, the device performance at room temperature was dominated by noise. The cause of increased noise is the associated decrease in contract magnetization. Since LSMO has a Tc that is only slightly higher than room temperature, the magnetization at room temperature is very small, thus reducing the signal. In our local device where both current and voltage are measured between the same two terminals, the resistance changed with time, resulting in increased noise. Consequently, the signal-to-noise ratio (SNR) is too small for acceptable sensor performance.

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Document Details

Document Type
Technical Report
Publication Date
Jun 01, 2011
Accession Number
ADA544912

Entities

People

  • Srini Krishnamurthy

Organizations

  • SRI International

Tags

Communities of Interest

  • Sensors

DTIC Thesaurus Topics

  • Charge Carriers
  • Critical Temperature
  • Curie Temperature
  • Detectors
  • Electrical Resistance
  • High Temperature
  • Magnetic Detection
  • Magnetic Detectors
  • Magnetic Fields
  • Magnetic Properties
  • Magnetoresistance
  • Materials
  • Precession
  • Quantum Properties
  • Resistance
  • Spin-Orbit Interaction
  • Transition Temperature

Readers

  • Research Science/Academic Research
  • Solar Photovoltaics and Thermoelectric Devices.
  • Thermal Physics or Thermal Science.

Technology Areas

  • Microelectronics
  • Microelectronics - Graphene