Thermal Resistance Between Powdered Cerium Magnesipm Nitrate and Liquid Helium at Very Low Temperatures

Experiments have been performed from magnetic temperatures of 2-20 mK on the effect of minute He-4 impurities and a magnetic field on the thermal resistance between powdered cerium magnesium nitrate (CMN) and liquid He-3. The thermal resistance decreases with decreasing T and increasing small field but is increased dramatically at a given T by the addition of roughly a monolayer of He-4. The resistance is interpreted as resulting from a surface magnetic coupling between CMN and liquid He-3.