Mechanism of carrier doping induced magnetic phase transitions in two-dimensional materials

TL;DR

This paper uncovers the mechanisms behind carrier doping-induced magnetic phase transitions in 2D semiconductors, linking electronic structure to magnetic order changes and enabling targeted design of magnetic heterostructures.

Contribution

It introduces a model based on first-principles simulations that classifies 2D magnetic semiconductors by their PDOS and predicts doping-induced magnetic phase transitions.

Findings

Different PDOS types correspond to specific magnetic transitions.

Critical doping densities can be quantitatively predicted.

The model aligns well with existing measurements.

Abstract

Electrically tuning long-range magnetic orders has been realized in two-dimensional (2D) semiconductors via electrostatic doping. On the other hand, the observations are highly diverse: the transition can be realized by either electrons or holes or both depending on specific materials. Moreover, doped carriers seem to always favor the ferromagnetic (FM) ground state. The mechanism behind those diverse observations remains uncovered. Combining first-principles simulations, we analyze the spin superexchange paths of the correlated d/f orbitals around band edges and assign 2D magnetic semiconductors into three types by their projected density of states (PDOS). We find that each type of PDOS corresponds to a specific carrier-driven magnetic phase transition and the critical doping density and type of carriers can be quantitatively obtained by calculating the superexchange coupling strength. The model results are in good agreements with first-principles calculations and available measurements. After understanding the mechanism, we can design heterostructures to realize the FM to antiferromagnetic transition, which has not been realized before. This model is helpful to understand diverse measurements and expand the degrees of freedom to control long-range magnetic orders in 2D semiconductors.