Millikelvin Diamond Anvil Cell for the Study of Quantum Critical Phenomena

We have developed a diamond anvil cell in which the force generation mechanism, a helium pressurised bellows, can be operated at low temperature to give in-situ pressure variation at pressures of up to 500 kbar at millikelvin temperatures. The novel coupling of the force generation bellows to the cell thermally isolates it from the mixing chamber of the dilution fridge, as well as allowing the cell to be used in the small bore of a high field magnet. AC-susceptibility measurements have been made for the first time using a low temperature impedance matching in conjunction with high-stability electronic compensation, yielding a measure close to the true sample susceptibility.