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MnBi₂Te₄ is an intrinsic magnetic topological insulator^1-3, which can support various topological quantum states, including QAHI, axion insulator, and an ideal Weyl semimetal (WSM)^4-6. In this talk, we report systematic c-axis transport studies on Mn(Bi_1-xSb_x)₂Te₄ under fields up to 35T. We found that the electronic anisotropy and spin-valve effect of this system are sensitively dependent on chemical potential, which can be tuned by Sb-content. The electronic anisotropy is remarkably enhanced as the chemical potential is close to the band edge, resulting in nonmetallic transport in the c-axis. Moreover, the electronic anisotropy increase results in a giant spin-valve effect in lightly electron-doped samples whose negative MR due to the spin flop transition reaches ~-95%. This is sharply contrasted with lightly hole-doped sample whose MR is dominated by chiral anomaly effect due to the presence of an ideal WSM, indicating Weyl fermions experience very weak magnetic scattering.

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4.Deng et al, Science 367, 895 (2020)

5.Liu et al, Nat. Mater. 19, 522 (2020)

6.Lee et al, PRX 11, 031032 (2021)