Ferromagnetism above 200 K in organic-ion intercalated CrSBr

TL;DR

This study demonstrates that intercalating organic ions into CrSBr transforms its magnetic order from antiferromagnetic to ferromagnetic, significantly raising the transition temperature above 200 K and enabling potential applications in high-temperature 2D magnetic devices.

Contribution

It introduces molecular intercalation as a novel method to tune and enhance the magnetic properties of CrSBr, achieving ferromagnetism above 200 K.

Findings

Intercalation induces a transition from antiferromagnetic to ferromagnetic order.

Magnetic transition temperatures are increased to 190 K and 230 K.

Intercalates exhibit large, hysteretic magnetoresistance exceeding 60% at 50 K.

Abstract

CrSBr is a van der Waals magnetic semiconductor exhibiting antiferromagnetic order below 140 K. It has emerged as a promising platform for engineering 2D magnetism because its intertwined electronic, optical, and magnetic properties can be profoundly modified via external stimuli such as electrical gating or magnetic fields. However, other strategies for tuning magnetism in layered materials, such as molecular intercalation, remain largely unexplored for CrSBr. Here, we demonstrate that the intercalation of tetramethylammonium (TMA) and tetrapropylammonium (TPA) ions into CrSBr induces a transition from antiferromagnetic to ferromagnetic order, while significantly enhancing the magnetic transition temperature to 190 K (TMA) and 230 K (TPA). The resulting intercalates are air-stable and exhibit large, hysteretic magnetoresistance exceeding 60% at 50 K in the TPA case. Besides, intercalation introduces symmetry-breaking structural changes in each CrSBr plane, revealed by Raman microscopy and corroborated by density functional theory (DFT) calculations. These findings highlight molecular intercalation as a powerful and versatile route to tailor the magnetic properties of CrSBr and unlock its potential to fabricate robust, high-temperature 2D magnetic devices.