High Accuracy Resisitivity and Temperature Coefficient Measurements of Invar Wire from 5K to 300K

The temperature coefficient of resistivity is a critical element of many AC-based hot-wire measurements of thermal properties. At cryogenic temperatures, most metallic materials suitable for wire and film-based forms have either a temperature coefficient or absolute resistivity that is too small to enable practical, accurate measurements. Invar (36Ni 64Fe) controlled thermal expansion alloy has a significant temperature coefficient of resistance while also maintaining significant absolute resistivity at cryogenic temperatures, and so has seen some use in low temperature 3-omega measurements. Prior data on the temperature coefficient of resistivity of Invar is limited and the uncertainty is high. In this work, we present high-accuracy resistance and temperature coefficient data for this material from 5-300 K.