Magnetic Susceptibility Measurements in Very Dilute Solid Solutions ofHe4inHe3

Measurements of the magnetic susceptibility of very dilute solid solutions of ${\mathrm{He}}^4$ in ${\mathrm{He}}^3$ as a function both of molar volume and of ${\mathrm{He}}^4$ concentration in the $\alpha$ phase have been made between 1 and 0.04°K by steady-state nuclear-resonance techniques. The most dilute solution (5 × ${10}^{-7\mathrm{}}$ ${\mathrm{He}}^4$) followed Curie's law over the range in molar volume (23.0-21.0 cc) measured. The less dilute solutions (1 × ${10}^{-4\mathrm{}}$ and 3 × ${10}^{-4\mathrm{}}$ ${\mathrm{He}}^4$) followed a Curie-Weiss law with relatively large, antiferromagnetic Weiss constants.