Intrinsic reduction of the ordered 4 f magnetic moments in semiconducting rare-earth nitride thin films: DyN, ErN, and HoN

Polarized neutron reflectometry and x-ray reflectometry were used to determine the nanoscale magnetic and chemical depth profiles of the heavy rare-earth nitrides HoN, ErN, and DyN in the form of 15-to 40-nm-thick films. The net ferromagnetic components are much lower than the predictions of density-functional theory and Hund's rules for a simple ferromagnetic ground state in these 4f ionic materials, which points to the intrinsic contribution of crystal-field effects and noncollinear spin structures. The magnetic moment per rare-earth ion was determined as a function of temperature in the range 5-100 K at fields of 1-4 T. It is demonstrated that the films are stoichiometric within 1-3% and magnetically homogeneous on the nanometer scale.