A method for accurate thermal conductivity measurements of small samples at ultra-low temperatures

A specific experimental arrangement has been developed for low temperature measurements of thermal conductivity of small samples such as single crystals of magnetic insulators with a typical length of a few millimeters. A frame of low conductance, serving as a mechanical support for ruthenium thermometers recording the temperature gradient on a sample, has been tested in the temperature range from 150 mK to 5 K by using commercial 99.95% purity polycrystalline non-annealed molybdenum. The applicability of the setup is discussed for the samples with the thermal conductance in the range 10−5–10−3 W/K.