SmN is a ferromagnetic semiconductor with the unusual property of an orbital-dominant magnetic moment that is largely cancelled by an antiparallel spin contribution, resulting in a near-zero net moment. However, there is a basic gap in the understanding of the ferromagnetic ground state, with existing density functional theory calculations providing values of the 4f magnetic moments at odds with experimental data. To clarify the situation, we employ an effective 4f Hamiltonian incorporating spin-orbit coupling, exchange, the crystal field, and J-mixing to calculate the ground state 4f moments. Our results are in excellent agreement with experimental data, revealing moderate quenching of both spin and orbital moments to magnitudes of ∼2μB in bulk SmN, enhanced to an average of ∼3μB in SmN layers within a SmN/GdN superlattice. These calculations provide insight into recent studies of SmN showing that it is an unconventional superconductor at low temperatures and displays twisted magnetization phases in magnetic heterostructures.
@article{arxiv.1511.04820,
title = {On the ferromagnetic ground state of SmN},
author = {J. F. McNulty and B. J. Ruck and H. J. Trodahl},
journal= {arXiv preprint arXiv:1511.04820},
year = {2016}
}