Saturation Magnetization and Ferromagnetic Interaction in Terbium Metal

The magnetic moment of terbium metal has been directly measured at 295°K, 100°K, 4.2°K, and 1.25°K in applied magnetic fields up to 70 000 gauss. In the liquid helium range, (∂M/∂T)H is zero. Between 35 000 gauss and 70 000, (∂M/∂H)T = (αβ2/ΔE) = 1.04×10−5 Bohr magneton per atom per gauss for 100°K and for the liquid helium range. At 1.25°K and 70 000 gauss, the magnetization is 7.5 Bohr magnetons per atom of terbium. This is perhaps near saturation. At 295°K the magnetization is linear up to about 45 000 gauss and shows a slight beginning saturation at higher fields. At 60 000 gauss the magnetization is 1.53 Bohr magnetons per atom of terbium. From the magnetization curve at 295°K (in the paramagnetic range) and a Brillouin function for the terbium atom in the F67 ground state, a molecular exchange field of 700 000 gauss is calculated. A sample motion ballistic technique is used to measure magnetic moments.