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 E_F ranging from 10 to 100 meV in the conduction band. Electrical, magnetic, and magneto-transport measurements reveal distinct behaviors depending on E_F. At lower E_F 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 E_F 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 E_F 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.