Physical Properties of Some Stoichiometric Rare Earth Nitride Single Crystals

摘要

The preparation and definition of large (3 - 5 mm edge length) single crystals of ScN, GdN, TbN, HoN, YbN and CeN is described. The Hall effect and the electrical conductivity are found to be metallic. The optical reflectivity between 30 meV (sometimes 1 meV) and 13 eV has been measured and the dielectric functions have been obtained. A plasma edge in the infrared confirms the metallic character. In GdN, a shift of this plasma edge with temperature through the magnetic ordering temperature has been observed as a new effect. GdN is in low magnetic fields antiferromagnetic, but becomes ferromagnetic in larger fields. The band structure is discussed. The magnetic exchange interactions have been derived. HoN in the relevant crystal directions has a spontaneous magnetic moment, but no saturation in fields up to 10 T. CeN is intermediate valent and exhibits a Pauli paramagnetism. The specific heat is measured down to 0.3 K and an enhanced?γ value is observed.