The spins of several resonances in the neutron cross section of gadolinium have been determined from measurements with polarized neutrons and polarized neuclei. Use was made of the difference in the statistical weighting factors to make the spin determinations absolute, i.e., independent of the sign of the nuclear hyperfine interaction or of any assumed directions.

Assuming $\frac{{\mu }^{155}}{{\mu }^{157}}=+0.750\mathrm{}$, the magnitude of the nuclear magnetic hyperfine interaction is determined to be $\frac{A}{k}=(8.0\mathrm{}\pm 0.8)\times {10}^{-4\mathrm{}}$ °K for ${\mathrm{Gd}}^{157}$ and (6.0±0.6)×${10}^{-4\mathrm{}}$°K for ${\mathrm{Gd}}^{155}$. If we assume the nuclear magnetic moment of ${\mathrm{Gd}}^{157}$ to be -0.33 nm we obtain a hyperfine magnetic field at the nucleus, $H_{\mathrm{hf}}=-(3.48+0.34)\mathrm{}\times {10}^5$ Oe.

• Received 2 February 1965

DOI:https://doi.org/10.1103/PhysRev.138.B1361