Magnetic Moments and Apparent Molecular Fields in Some Rare Earth Metals and Compounds

A study has been made of the absolute magnetization of some rare earth metals (gadolinium and cerium) and some compounds (ytterbium oxide, neodymium oxide, erbium oxide and yttrium iron garnet) as a function of magnetic fields up to 60 000 gauss and temperature down to 1.3°K. The saturation magnetization of ferromagnetic gadolinium is 7.05±0.10 Bohr magneton per atom of gadolinium and its molecular field is 1.3 megagauss. The average magnetization of cerium is only 0.17 Bohr magneton per atom of cerium even at 1.3°K and 60 000 gauss. It is ferrimagnetic with an estimated antiferromagnetic molecular field of one-half megagauss. Ytterbium sesquioxide has an antiferromagnetic molecular field of about 35 000 gauss and becomes antiferromagnetic at about 3°K in zero field. Yttrium iron garnet (YIG) has been studied and the saturation magnetization has been determined at 100°K and in the helium range. The saturation magnetization is 0.83 at 1.3°K as compared with 1.25 Bohr magnetons per atom of iron in gamma iron (III) oxide studied previously. A ballistic method was used for measuring the magnetic moment and the calibration was made using metallic iron.