Fluctuation-driven colossal magnetoresistance without magnetic polarization in the ferrimagnetic insulator Mn₃Si₂Te₆

Magnetic polarization is essential to colossal magnetoresistance (CMR) in almost all CMR materials, except for a few exceptions. Here we report a new type of CMR in the title compound that emerges only when magnetic polarization is avoided. The resistivity drops by 7 orders of magnitude when the magnetic field H is applied along the magnetic hard axis but only by 20% when H is aligned along with the magnetic easy axis, where the magnetization is fully polarized. The anisotropy field separating the easy and hard axes is 13 T, suggesting the strong effect of the spin-orbit interactions. Double exchange and Jahn-Teller distortions that drive the well-studied hole-doped manganites do not exist in Mn₃Si₂Te₆. The phenomena fit no existing models, suggesting a unique, intriguing type of electrical transport.