Coexisting Ferromagnetic-antiferromagnetic Phase and Manipulation in Magnetic Topological Insulator MnBi4Te7

TL;DR

This study uses cryogenic magnetic force microscopy to visualize and manipulate the complex magnetic phases in MnBi4Te7, revealing new insights into its magnetic behaviors and potential for local control of topological properties.

Contribution

It provides the first real-space visualization of multiple magnetic phases in MnBi4Te7 and demonstrates local phase manipulation using magnetic tips.

Findings

Sequential visualization of magnetic phases with increasing magnetic field.

Complete H-T phase diagram of MnBi4Te7.

Local phase transformation from AFM to FM using magnetic tip stray fields.

Abstract

Magnetic topological insulators (MTIs) have received a lot of attention due to the existence of various quantum phenomena such as quantum anomalous Hall effect (QAHE) and topological magnetoelectric effect, etc. The intrinsic superlattice-like layered MTIs, MnBi2Te4/(Bi2Te3)n, have been extensively investigated mainly through the transport measurements, while the direct investigation of their superlattice-sensitive magnetic behaviors is relatively rare. Here, we report a microscopic real-space investigation of magnetic phase behaviors in MnBi4Te7 using cryogenic magnetic force microscopy (MFM). The intrinsic robust A-type antiferromagnetic (AFM), and emerged surface spin-flop (SSF), canted AFM (CAFM), ferromagnetic (FM)+CAFM, forced FM phases are sequentially visualized via the increased external magnetic field, in agreement with the metamagnetic behavior in the M-H curve. The temperature-dependent magnetic phase evolution behaviors are further investigated to obtain the complete H-T phase diagram of MnBi4Te7. The tentative local phase manipulation via the stray field of the magnetic tip is demonstrated by transforming the AFM to FM phase in its surface layers of MnBi4Te7. Our study the not only provide key real-space ingredients for understanding their complicated magnetic, electronic, and topological properties of these intrinsic MTIs, but also suggest new directions for manipulating spin textures and locally controlling their exotic properties.