Magnetic Structure and Spin Fluctuations in Colossal Magnetoresistance Ferrimagnet Mn3Si2Te6

TL;DR

This study uncovers the magnetic structure and spin fluctuations in Mn3Si2Te6, revealing their significant role in its colossal magnetoresistance, with insights gained from neutron diffraction and correlation with electrical resistivity.

Contribution

It provides the first detailed magnetic structure and spin fluctuation analysis of Mn3Si2Te6, linking magnetic behavior to its colossal magnetoresistance phenomenon.

Findings

Noncollinear magnetic structure with moments mainly in the basal plane

Persistent magnetic diffuse scattering above Tc

Spin fluctuations correlate with resistivity near the transition

Abstract

The ferrimagnetic insulator Mn3Si2Te6, which features a Curie temperature Tc at 78 K and a delicate yet consequential magnetic frustration, exhibits colossal magnetoresistance (CMR) when the magnetic field is applied along the magnetic hard axis, surprisingly inconsistent with existing precedents [Y. Ni, H. Zhao, Y. Zhang et al. Phys. Rev. B 103, L161105 (2021)]. This discovery motivates a thorough single-crystal neutron diffraction study in order to gain insights into the magnetic structure and its hidden correlation with the new type of CMR. Here we report a noncollinear magnetic structure below the Tc where the moments lie predominantly within the basal plane but tilt toward the c axis by ~10o at ambient conditions. A substantial magnetic diffuse scattering decays slowly and persists well above the Tc. The evolution of the spin correlation lengths agrees well with the electrical resistivity, underscoring the role of spin fluctuation contributing to the magnetoresistivity near the transition. Application of magnetic field along the c axis, renders a swift occurrence of CMR but only a slow tilting of the magnetic moments toward the c axis. The unparalleled changes indicate a non-consequential role of magnetic polarization.