Electronic transport properties of speer carbon resistor - Experimental results and semi-empirical fits

Rachel Rosenbaum, G. E. Jones, T. Murphy

Research output: Contribution to journalArticlepeer-review

Abstract

Speer carbon composition resistors, in particular the 470 Ω and 220 Ω 1/2 W grade 1002 resistors, have been used as secondary thermometers at temperatures below 4 K for many years. Their zero field resistances have been measured between 300 K and 4 K using a "dip" probe. Above 10 K, the resistance behavior can be explained using a simple temperature power law, R(T) ≈ R0/T 0.16. The resistance measurements have been extended to 0.02 K using dilution refrigerators. Between 4 K and 0.3 K, the resistances exhibited activated laws having hopping exponents y ≈ 0.5. Below 0.3 K, the 470 Ω resistors exhibit a crossover to a weaker activated law. Crossover resistance expressions suggest that the resistances follow a Mott variable-range hopping (VRH) law below 0.05 K. The low temperature magnetoresistance (MR) data showed changes of less than ±12 % of the zero field resistance values in fields up to 10 T. Fits using the wave function shrinkage and the forward interference models gave only fair agreement with the MR data.

Original languageEnglish
Pages (from-to)439-459
Number of pages21
JournalJournal of Low Temperature Physics
Volume139
Issue number3-4
DOIs
StatePublished - May 2005

Keywords

  • Activated and variable-range hopping (VRH) resistance laws
  • Low temperature thermometry
  • Magnetoresistance(MR)
  • Speer carbon resistors

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