Electrically Controlled Anomalous Hall Effect and Orbital Magnetization in Topological Magnet MnBi_{2}Te_{4}

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Phenomena

Background:

• The even-odd effect in magnetic topological materials is not fully understood.
• MnBi_{2}Te_{4} is a promising material for exploring quantum phenomena due to its intrinsic magnetic topological properties.

Purpose of the Study:

• To elucidate the intrinsic mechanism behind the even-odd effect in electron-doped MnBi_{2}Te_{4} thin films.
• To explain the observed opposite signs of anomalous Hall resistance and distinct hysteresis loop shapes in even and odd septuple layers (SLs).

Main Methods:

• Molecular beam epitaxy (MBE) growth of MnBi_{2}Te_{4} thin films with electron doping.
• Anomalous Hall effect (AHE) measurements.
• Magnetic circular dichroism (MCD) measurements.
• Theoretical modeling of magnetic transitions and surface states.

Main Results:

• Identified two distinct antiferromagnetic (AFM) configurations in even-SL MnBi_{2}Te_{4} films, leading to different zeroth Landau level energies of surface states.
• Observed nonzero hysteresis loops in AHE and MCD for even-SLs, attributed to transitions between AFM states and a subsequent transition to a ferromagnetic state.
• Established a clear relationship and distinction between the axion parameter and magnetoelectric coefficient.
• Demonstrated an even-odd oscillation behavior of magnetoelectric coefficients in MnBi_{2}Te_{4} films.

Conclusions:

• The even-odd effect in MnBi_{2}Te_{4} is intrinsically linked to competing AFM states and their influence on surface electronic states.
• The proposed model successfully explains the complex AHE hysteresis loops and provides insights into magnetoelectric properties.
• This work advances the understanding of magnetic topological materials and their potential applications.