MAGNETIC COUPLING IN THERMAL-BOUNDARY RESISTANCE BETWEEN THIN SILVER FILMS AND LIQUID-HE-3 IN THE MILLIKELVIN REGIME

Using a glass-capacitance technique, we have measured the thermal-boun dary resistance R(K) between liquid He-3 and thin silver films on a fl at glass substrate in the millikelvin regime. For T>30 mK, the experim ental observations are in excellent agreement with the acoustic mismat ch theory. For T<30 mK, we find concrete evidence supporting the magne tic coupling mechanism: (i) observation of a minimum in R(K) as a func tion of magnetic field, (ii) a decrease in R(K) as He-3 pressure is in creased, and (iii) a nearly order-of-magnitude increase in R(K) result ing from preplating the silver surface with monolayers of He-4 (with n o such effect at T>30 mK).