Development of Copper Powder Demagnetization Stage Compatible with Cryogen-free Cryostats

Motivated by demand to investigate two-dimensional electron systems (2DES) at ultra-low, electron temperatures below 10 mK, our goal is to develop compact, modular cells that ensure proper thermalization of the on-chip electrons within nano-sized devices down to 1 mK and in sizeable magnetic fields ≥ 1 T. The approach involves an "in-cell" magnetic cooling platform compatible with the cryogen-free dilution cryostats. This method entails immersing copper powder directly into liquid ³He, which serves as a coupling agent between the refrigerant, the electrical contacts, and the on-chip electrons. Avoiding bulk copper in the magnetic field required for traditional demag systems eliminates most of the eddy current heating resulting from Pulse Tube vibrations, while also reducing the demag time. This approach has been used in "wet" dilution cryostats to study quantum fluids [1], but its adaptation to cryogen-free systems is novel. Ultimately, the sample response is studied while both magnetic filed and temperature are changing, and the results of numerical simulations and experimental findings will be presented.

[1] R.C.M. Dow, et al. J Low Temp Phys 47 (1982) 477; D.I. Bradley, et al. J Low Temp Phys 57 (1984) 359.