Gate-tunable magnetoresistance in six-septuple-layer MnBi2Te4

The recently discovered antiferromagnetic topological insulator MnBi2Te4 hosts many exotic topological quantum phases such as the axion insulator and Chern insulator. Here we report systematic gate voltage dependent magneto transport studies in six septuple-layer MnBi2Te4. In p-type carrier regime, we observe positive linear magnetoresistance when MnBi2Te4 is polarized in the ferromagnetic state by an out-of-plane magnetic field. Whereas in the n-type regime, distinct negative magnetoresistance behaviors are observed. The behaviors of magnetoresistance in both regimes are highlyrobust against temperature up to the Néel temperature. Within the antiferromagnetic regime, the behavior of magnetoresistance exhibits a transition from negative to positive under the control of gate voltage. The boundaries of the magnetoresistance phase diagram can be explicitly marked by the gate-voltage-independent magnetic fields that characterize the processes of the spin-flop transition. The rich transport phenomena demonstrate the intricate interplay between topology, magnetism and dimensionality in MnBi2Te4.

Giant linear magnetoresistance in half-metallic Sr2CrMoO6 thin films

Linear magnetoresistance (LMR) is a special case of a magnetic-field induced resistivity response, which has been reported in highly disordered semiconductor systems and in topological materials. In this work, we observe LMR effect in half-metallic perovskite Sr2CrMoO6 thin films, of which the maximum MR value exceeds +1600% at 2 K and 14 T. It is an unusual behavior in ferrimagnetic double perovskite material like Sr2CrMoO6, which are known for intrinsic tunneling-type negative magnetoresistance. In the thin films, the high carriers’ density (~1022 cm−3) and ultrahigh mobility (~104 cm2 V−1 s−1) provide a low-resistivity (~10 nΩ·cm) platform for spin-polarized current. Our DFT calculations and magnetic measurements further support the half-metal band structure. The LMR effect in Sr2CrMoO6 could possibly originate from transport behavior that is governed by the guiding center motion of cyclotron orbitals, where the magnetic domain structure possibly provides disordered potential. The ultrahigh mobility and LMR in this system could broaden the applications of perovskites, and introduce more research on metallic oxide ferri-/ferro-magnetic materials.