Strong Field Magnetization at Low Temperatures and Approach to Absolute Saturation of Thulium Metal

Magnetization studies of metallic thulium have been carried out at low temperatures and in magnetic fields up to 70 000 gauss. Near 100°K, the magnetization $\mathrm{(M)}$ is linear in field and reaches 0.8 Bohr magnetons per atom of thulium at 70 000 gauss. At 4.2°K, a magnetization curve is traced in which the direction of concavity changes twice. In the high field range, $\mathrm{(\partial M/\partial H)}$ is decreasing and between 60 000 and 70 000 gauss, it is very small. At 70 000 gauss, the magnetization reaches 3.4 Bohr magnetons per atom of thulium, suggesting the validity of the ${}^2{F}_{\text{7/2}}$ ground state assignment for metallic thulium. At 1.3°K, the magnetization is slightly lower at equivalent fields, but approaches the same 70 000 gauss value as at 4.2°K. The remanence is 0.3 Bohr magneton per atom at 4.2°K and 0.4 Bohr magneton per atom at 1.3°K. A pronounced hysteresis is observed in the liquid helium range. A sample motion technique is used in the measurements and the calibration carried out with pure nickel.