# Mechanism of Anomalous Anisotropic Colossal Magnetoresistance in Quasi‐2D Mn3Si2Te6 Bulk Single Crystal

## TL;DR

This paper investigates the unusual magnetoresistance in a 2D-like magnetic material and proposes a new model to explain its behavior, which could be useful for spintronic devices.

## Contribution

A novel model is proposed to explain the anisotropic colossal magnetoresistance in Mn3Si2Te6 single crystals.

## Key findings

- Magnetoresistance in Mn3Si2Te6 shows no saturation in the ab-plane but reaches ≈−100% along the c-axis below the Curie temperature.
- A new model suggests that in-plane fields induce 2D transport while out-of-plane fields promote 3D transport.
- Alignment of spin-polarized carriers with magnetic moments significantly suppresses scattering when the c-axis field exceeds the demagnetizing field.

## Abstract

Mn3Si2Te6, quasi‐2D ferrimagnetic semiconductor, exhibits anomalous saturated colossal magnetoresistance (CMR) only when a magnetic field is applied along its magnetic hard magnetization axis, suggesting unconventional underlying physics and promising potential for spintronic applications. However, the intrinsic mechanism behind this anomalous anisotropic CMR remain unresolved. In this work, the temperature and angular dependencies of magnetoresistance (MR) in high‐quality Mn3Si2Te6 single crystals are systematically investigated. The MR measured within the easy ab‐plane shows no saturation, whereas a large negative saturation MR of ≈ −100% is observed along the hard magnetization c‐axis below the Curie temperature. To explain this behavior, a novel model is proposed in which in‐plane magnetic fields induce quasi‐2D magnetotransport, while out‐of‐plane fields promote a transition to 3D transport. Notably, when the c‐axis field exceeds the demagnetizing field, the alignment between spin‐polarized carriers and magnetic moments significantly suppresses scattering. The results challenge the applicability of the chiral orbital currents (COC) model in Mn3Si2Te6 single crystals and establish a new framework for controlling the CMR effect in layered magnets, offering a pathway toward future spintronic technologies.

The external field exceeds Hd, the speed polarization abruptly reorients to align with the Mn magnetic moments, leading to an MR ≈ −100%.