Phase Diagram of LiquidHe3between 0.7 and 2.5 mK

We describe a nuclear demagnetization cryostat in which liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ has been cooled to below 0.7 mK. Data on the boundaries between the normal Fermi-liquid and the superfluid phases of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, as determined from NMR measurements, are presented between 0.7 and 2.5 mK and from 0 to 27 bar. The "$\lambda$ point" of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ was found at 0.93 mK.