Twisted phase of the orbital-dominant ferromagnet SmN in a GdN/SmN heterostructure

• Published in: Physical review. B, Condensed matter and materials physics Vol. 91; no. 17
• Main Authors: McNulty, J. F., Anton, E.-M., Ruck, B. J., Natali, F., Warring, H., Wilhelm, F., Rogalev, A., Soares, M. Medeiros, Brookes, N. B., Trodahl, H. J.
• Format: Journal Article
• Language: English
• Published: 22-05-2015
• Subjects: Condensed matter; Ferromagnetism; Heterostructures; Magnetic moment; Magnetization; Orbitals; Rare earth metals; Transition metals
• ISSN: 1098-0121; 1550-235X
• DOI: 10.1103/PhysRevB.91.174426

The strong spin-orbit interaction in the rare-earth elements ensures that even within a ferromagnetic state there is a substantial orbital contribution to the ferromagnetic moment, in contrast to more familiar transition metal systems in which the orbital moment is usually quenched. The orbital-dominant magnetization that is then possible within rare-earth systems facilitates the fabrication of entirely new magnetic heterostructures, and here we report a study of a particularly striking example comprising interfaces between GdN and SmN. Our investigation reveals a twisted magnetization arising from the large spin-only magnetic moment in GdN and the nearly zero, but orbital-dominant, moment of SmN. The unusual twisted phase is driven by (i) the similar ferromagnetic Gd-Gd, Sm-Sm, and Gd-Sm exchange interactions, (ii) a SmN Zeeman interaction 200 times weaker than that of GdN, and (iii) the orbital-dominant SmN magnetic moment. The element specificity of x-ray magnetic circular dichroism is used in separate modes probing both bulk and surface regions, revealing the depth profile of the twisting magnetization.