Nuclear Polarization in Polycrystalline Holmium-Indium Alloy

Holmium and indium nuclei have been polarized by nuclear hyperfine interaction in a polycrystalline ferromagnetic alloy, 92.2% holmium-7.8% indium. The nuclear polarization for each constituent was determined from the transmission of monochromatic, polarized neutron beams at neutron energies corresponding to resonances in the holmium and indium cross sections. A series of measurements at several temperatures from 0.071 to 4.225°K yield the following values for the hyperfine constant: for holmium, $\frac{A}{k}=0.58\mathrm{}\pm 0.03°$K (corresponding to an effective field at the nucleus, $H_{\mathrm{eff}}=+8.4\mathrm{}\times {10}^6$ Oe); and for In, $\frac{A}{k}=-0.013\mathrm{}\pm 0.002°$K (corresponding to $H_{\mathrm{eff}}=-1.3\mathrm{}\times {10}^5$ Oe). The effect on the nuclear polarization of the magnetic anisotropy of the polycrystalline sample is discussed.