Even-Odd Layer-Dependent Exchange Bias Effect in MnBi₂Te₄ Chern Insulator Devices

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Phenomena

Background:

• Magnetic topological materials host exotic quantum effects like the quantum anomalous Hall effect.
• MnBi₂Te₄ is an antiferromagnetic topological insulator with unique layer-dependent properties.

Purpose of the Study:

• Investigate the even-odd layer-dependent physics of MnBi₂Te₄ thin flakes.
• Understand the origin of the observed exchange bias effect.

Main Methods:

• Fabrication of MnBi₂Te₄ thin-flake devices using stencil masks.
• Magnetic field training and electrical transport measurements.
• First-principles theoretical calculations.

Main Results:

• Observation of the Chern insulator state in MnBi₂Te₄ thin flakes at high magnetic fields.
• Significant exchange bias effect in odd septuple layer (SL) devices, absent in even SL devices, after magnetic field training.
• Theoretical attribution of the exchange bias to contrasting surface and bulk magnetic properties.

Conclusions:

• The study reveals the microscopic magnetic configuration of MnBi₂Te₄ thin flakes.
• Even-odd layer-dependent magnetic properties are confirmed.
• Challenges for achieving the zero magnetic field quantum anomalous Hall effect in odd SL MnBi₂Te₄ are highlighted.