Resistance Minimum of Magnesium: Electrical and Thermal Resistivities

Abstract

The thermal and electrical resistivities of two specimens of magnesium have been measured in the temperature range 1.5 to 25\ifmmode^\circ\else\textdegree\fi{}K. One specimen was a spectrographically pure rod of 99.98+% magnesium with 0.013% iron as the major contamination. The second specimen was 99.95+% pure with 0.043% manganese as the only significant contaminant. The electrical resistivity of the purer material passed through a minimum at \ensuremath{\sim}5\ifmmode^\circ\else\textdegree\fi{}K and increased by 1.7% as the temperature was lowered to 1.5\ifmmode^\circ\else\textdegree\fi{}K. In the same specimen, the thermal resistivity at the lowest temperature exhibited a positive deviation from normal behavior (defined by $w=\ensuremath{\alpha}{T}^{2}+\frac{\ensuremath{\beta}}{T}$) of the same order of magnitude. Between 5\ifmmode^\circ\else\textdegree\fi{} and 15\ifmmode^\circ\else\textdegree\fi{}K a negative deviation was observed in the thermal resistivity.The electrical resistivity of the dilute manganese alloy specimen passed through a minimum at \ensuremath{\sim}14\ifmmode^\circ\else\textdegree\fi{}K and increased by approximately 20% as the temperature was lowered to 1.5\ifmmode^\circ\else\textdegree\fi{}K. An exactly analogous effect was found in the thermal resistivity as evidenced by (1) a constant Lorenz ratio at temperatures below 4\ifmmode^\circ\else\textdegree\fi{}K, and (2) the equality of the percentage deviations of the respective resistivities from normal behavior over the entire range of measurements.