The Magnetic Properties of Selected Rare Earth Nitrides Grown by Pulsed Laser Deposition

Gadolinium nitride (GdN) and samarium nitride (SmN) are grown by pulsed laser deposition on yttria stabilised zirconia substrates.  Surface and structural characterisation shows that the thin films are epitaxial with crystallites of up to 30 nm in diameter and a very large in plane coherence length. A novel oxide layer is observed at the substrate-film interface, caused by oxygen in the substrate reacting with the deposited rare earth element. GdN is found to be ferromagnetic below 70 K with a saturation moment of 7 Bohr magneton per ion. The relationship between the crystal structure and the magnetisation is investigated using ferromagnetic resonance and a weak easy axis along the [111] azimuth is reported. Hall effect measurements show the carriers are electrons, present in concentrations of 1020/cm3. Magnetic measurements on SmN show the presence of metallic droplets, but correcting for these, the Curie temperature is found to be 30 K.We report on preliminary growths of europium nitride and show the valence of the Eu is 3+, solving an outstanding theoretical question.