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

TL;DR

This study uncovers a twisted magnetic phase at GdN/SmN interfaces driven by the interplay of exchange interactions and orbital-dominant magnetization, revealing new magnetic behaviors in rare-earth heterostructures.

Contribution

It demonstrates the existence of a twisted magnetization phase in GdN/SmN heterostructures caused by orbital-dominant moments and weak Zeeman interactions, a novel phenomenon in rare-earth magnetic interfaces.

Findings

Identification of a twisted magnetization phase at GdN/SmN interfaces.

Element-specific depth profiling of the magnetization twist.

Role of orbital dominance and weak Zeeman interaction in the twist.

Abstract

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, where 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 ferromag- netic 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 (XMCD) is used in seperate modes probing both bulk and surface regions, revealing the depth profile of the twisting magnetization.