Magnetic Amplification at Yb3+ "Designer Defects" in the van der Waals Ferromagnet, CrI3

TL;DR

This study demonstrates how Yb3+ optical impurities in 2D CrI3 ferromagnets act as 'designer defects' that reveal and influence magnetic properties through magneto-photoluminescence, enabling new functionalities in 2D magnetic materials.

Contribution

It introduces Yb3+ as a magnetic optical impurity in CrI3, showing how it can be used to probe and control magnetic interactions in 2D ferromagnets.

Findings

Yb3+ magnetization is pinned to CrI3 magnetization.

Effective internal field of ~10 T at Yb3+ due to superexchange.

Yb3+ PL energy reflects high covalency and magnetic ordering.

Abstract

The two-dimensional (2D) van der Waals ferromagnet CrI3 has been doped with the magnetic optical impurity Yb3+ to yield materials that display sharp multi-line Yb3+ photoluminescence (PL) controlled by the magnetism of CrI3. Magneto-PL shows that Yb3+ magnetization is pinned to the magnetization of CrI3. An effective internal field of ~10 T at Yb3+ is estimated, attributed to strong in-plane Yb3+-Cr3+ superexchange coupling. The anomalously low energy of Yb3+ PL in CrI3 reflects relatively high Yb3+-I- covalency, contributing to Yb3+-Cr3+ superexchange coupling. The Yb3+ PL energy and linewidth both reveal the effects of spontaneous zero-field CrI3 magnetic ordering within 2D layers below TC, despite the absence of net magnetization in multilayer samples. These results illustrate the use of optical impurities as "designer defects" to introduce unique functionality to 2D magnets.