Researchers Enhance 2D Ferromagnetism for Quantum Devices

Scientists have made significant advancements in the field of two-dimensional (2D) ferromagnetism by layering a 2D ferromagnetic material with a topological insulator. This innovative approach enhances the material’s magnetic properties, making it a promising candidate for next-generation quantum devices.

Researchers focused on the properties of the material known as Cr2Te3, which has a crystal structure that forms naturally occurring layers resembling 2D sheets of magnetic material. Each layer of Cr2Te3 exhibits ferromagnetism, but the layers are not tightly bound in the third dimension, classifying them as “quasi-2D.” This characteristic allows for effective interface engineering, opening up new avenues for exploring quantum phenomena.

Utilizing a technique called molecular beam epitaxy, which allows for atomically precise thin-film growth, the team successfully synthesized Cr2Te3 down to monolayer thickness on insulating substrates at a wafer scale. Remarkably, the ferromagnetic properties of the material remained intact even at the monolayer level, representing a critical achievement for the field of 2D magnetism.

The researchers found that when Cr2Te3 was placed in close contact with a topological insulator, specifically (Bi,Sb)2Te3, the Curie temperature—the point at which materials transition from ferromagnetic to paramagnetic—rose significantly from approximately 100 K to 120 K. This enhancement was confirmed through polarized neutron reflectometry, which demonstrated a substantial increase in magnetization at the interface.

Theoretical models suggest that this increase in magnetization is due to the Bloembergen–Rowland interaction, a long-range exchange mechanism that is mediated by virtual intraband transitions. This interaction is facilitated by the topological insulator’s topologically protected surface states, which are spin-polarized and resilient against disorder. These states enable long-distance magnetic coupling across the interface, indicating a universal mechanism for enhancing Curie temperatures in topological insulator-coupled magnetic heterostructures.

This research not only highlights a method for stabilizing 2D ferromagnetism but also paves the way for advancements in topological electronics. By co-engineering magnetism and topology at the interface, the findings could lead to the development of novel quantum hybrid devices. Potential applications include spintronic components, topological transistors, and platforms that could realize exotic quasiparticles like Majorana fermions.

The findings of this study will be published in Rep. Prog. Phys. in 2025. The work represents a significant step forward in understanding the interactions between different material properties and their implications for future technology.