抄録
The adiabatic magnetization curves have been measured on single crystals of NiSiF6·6H2O and CuSiF6·6H2O using a Cioffi-type recording flux-meter. The specific heats have also been determined. Nickel fluosilicate was found to be ferromagnetic with the easy axis parallel to the c-axis. The magnetic Curie temperature is about 0.15°K while the specific heat maximum is at 0.135°K. The magnetic behaviour of copper fluosilicate is ferromagnetic and nearly isotropic. The magnetic Curie temperature is about 0.07°K. The entropy versus temperature curve has a kink at 0.10°K (at an entropy value of 0.46 R) showing the ordering in two steps. Weiss constants were determined at helium temperatures; θ⁄⁄−+0.15°K, θ⊥−+0.08°K for nickel salt; and θ(powder)=+0.07°±0.02°K, θ⁄⁄c=+0.08°±0.02°K, θ⊥c=0.05°±0.02°K, and g(powder)=2.25, g⁄⁄c=2.25, g⊥c=2.26(mean values) for copper salt.
