Researchers Enhance 2D Ferromagnetism for Quantum Devices

Researchers have successfully enhanced the properties of a two-dimensional (2D) ferromagnetic material, paving the way for advancements in next-generation quantum devices. By layering the material, specifically Cr2Te3, with a topological insulator, they demonstrated a notable increase in its magnetic capabilities, revealing a promising approach for future technological applications.

The study, led by Yunbo Ou and published in Rep. Prog. Phys. in 2025, explores how exchange-coupled interfaces can stabilize and amplify ferromagnetic characteristics in 2D materials like transition metal chalcogenides. These materials possess intricate interactions among charge, spin, orbital, and lattice degrees of freedom, making them an intriguing focus for emergent quantum phenomena.

Advancements in 2D Magnetism

The crystal structure of Cr2Te3 naturally forms layers that act as quasi-2D sheets of magnetic material. While each layer exhibits ferromagnetism, they are not tightly bonded in the third dimension, allowing for effective interface engineering. Using a vacuum-based technique known as molecular beam epitaxy, the team achieved wafer-scale synthesis of Cr2Te3 down to monolayer thickness on insulating substrates. Remarkably, robust ferromagnetism remains intact even at the monolayer limit, a significant milestone for 2D magnetism.

When Cr2Te3 is brought into close contact with a topological insulator—specifically, (Bi,Sb)2Te3—the Curie temperature, which marks the transition between ferromagnetic and paramagnetic states, increases from approximately 100 K to 120 K. This enhancement has been experimentally verified through polarized neutron reflectometry, demonstrating a substantial boost in magnetization at the interface.

Significance of Topological Insulators

Theoretical models attribute this magnetic enhancement to the Bloembergen–Rowland interaction, a long-range exchange mechanism mediated by virtual intraband transitions. This interaction is notably supported by the topologically protected surface states of the topological insulator, which are spin-polarized and resilient against disorder. These states enable long-distance magnetic coupling across the interface, suggesting a universal mechanism for enhancing the Curie temperature in topological insulator-coupled magnetic heterostructures.

The implications of this research extend beyond stabilizing 2D ferromagnetism. It opens avenues for developing topological electronics, wherein magnetism and topology can be co-engineered at the interface. Such systems have the potential to facilitate novel quantum hybrid devices, including spintronic components, topological transistors, and platforms for realizing exotic quasiparticles such as Majorana fermions.

This groundbreaking work not only demonstrates a method for enhancing ferromagnetic properties but also signifies a step forward in the convergence of magnetism and topology in quantum technologies. The ability to manipulate magnetic properties at such a fundamental level could lead to significant advancements in the field of quantum computing and beyond.