The delicate coupling between magnetism and magneto-transport in Fermi-energy-adjusted MnBi2Te4 crystals

We explored the coupling between magnetic and magneto-transport properties in MnBi2Te4 crystals with Fermi energy EF ranging from 10 to 100 meV in the conduction band. Electrical, magnetic, and magneto-transport measurements reveal distinct behaviors depending on EF. At lower EF values (10 meV), MnBi2Te4 exhibits degenerate-semiconductor-like electrical transport and ferrimagnetism, with weak coupling between magneto-resistance and ferrimagnetism. In contrast, MnBi2Te4 displays metallic transport and antiferromagnetism (AFM) at higher Fermi energies, with magneto-resistance strongly coupled to antiferromagnetism and canted antiferromagnetism under a large external magnetic field. Remarkably, Hall measurements demonstrate a pronounced anomalous Hall resistivity (AHR) when the EF of MnBi2Te4 is 10 meV, larger than that reported for other bulk MnBi2Te4 crystals in the literature. Significant AHR is attributed to the Berry-phase effect in electronic-band structure based on first-principles calculation. The evolution of magnetic and magneto-transport properties in EF shifted MnBi2Te4 can be semi-quantitatively explained by the Ruderman–Kittel–Kasuya–Yosida interaction between neighboring MnTe layers. Our work suggests that the strongly Fermi-energy-sensitive magneto-transport properties observed in MnBi2Te4 may be useful in developing magnetic sensors/detectors.