Pressure-tuned intralayer exchange in superlattice-like MnBi2Te4/(Bi2Te3)n topological insulators

TL;DR

This study demonstrates how hydrostatic pressure can tune intralayer exchange interactions in MnBi2Te4/(Bi2Te3)n topological insulators, inducing magnetic phase transitions and revealing the robustness of intralayer ferromagnetic coupling.

Contribution

It uncovers pressure-induced magnetic phase transitions in MnBi2Te4/(Bi2Te3)n, highlighting the role of intralayer exchange coupling in magnetic control of topological insulators.

Findings

MnBi4Te7 remains A-type AFM with decreasing Ne9el temperature under pressure.

MnBi6Te10 transitions from A-type AFM to quasi-2D FM state under pressure.

Lattice compression influences intralayer exchange coupling, driving magnetic phase changes.

Abstract

The magnetic structures of MnBi2Te4(Bi2Te3)n can be manipulated by tuning the interlayer coupling via the number of Bi2Te3 spacer layers n, while the intralayer ferromagnetic (FM) exchange coupling is considered too robust to control. By applying hydrostatic pressure up to 3.5 GPa, we discover opposite responses of magnetic properties for n = 1 and 2. MnBi4Te7 stays at A-type antiferromagnetic (AFM) phase with a decreasing N\'eel temperature and an increasing saturation field. In sharp contrast, MnBi6Te10 experiences a phase transition from A-type AFM to a quasi-two-dimensional FM state with a suppressed saturation field under pressure. First-principles calculations reveal the essential role of intralayer exchange coupling from lattice compression in determining these magnetic properties. Such magnetic phase transition is also observed in 20% Sb-doped MnBi6Te10 due to the in-plane lattice compression.