Cryogen-free one hundred microKelvin refrigerator

Temperature below 100 μK is achieved in a customized cryogen-free dilution refrigerator with a copper-nuclear demagnetization stage. The lowest temperature of conduction electrons of the demagnetization stage is below 100 μK as measured by a pulsed platinum NMR thermometer and the temperature can remain below 100 μK for over 10 hours. 9 T demagnetization magnetic field and 12 T research magnetic field can be controlled independently, provided by a coaxial room-temperature-bore cryogen-free magnet.