Abstract
Measurements of the planar Hall effect (PHE) and anisotropic magnetoresistance (AMR) in polycrystalline films of topological insulator Bi85Sb15 are reported. The observation of PHE and AMR in these films of carrier density ≈2 × 1019 electrons/cm3 is like the behavior of in-plane field transport in thin films of metallic ferromagnets. However, the amplitudes of PHE (ΔρPHE) and AMR (Δρxx) are at variance. ΔρPHE and Δρxx also undergo a sign reversal near ≈160 K. We compare these results with the reported PHE of topological insulators and Weyl semimetals and discuss possible scenarios for anisotropic backscattering of charge carriers in this non-magnetic alloy.
Highlights
Bismuth–antimony alloys (Bi1−xSbx) are well-known thermoelectric (TE) materials.1,2 Their TE characteristics emanate from a tunable electronic band structure achieved by adjusting the Bi/Sb ratio in the alloy
Due to the low melting points of Bi and Sb, the growth or annealing of BiSb films at T > TLiquidus may result in phase separation; we have deposited the films at only T < 150 ○C
The experimental data of Taskin et al.20 on the (Bi1−xSbx)2Te3 crystal show a large difference in ΔRPHE and ΔRxx, which the authors have attributed to a contamination of the signal by an OMR contribution arising from the misalignment of the sample plane and the plane of rotation
Summary
Bismuth–antimony alloys (Bi1−xSbx) are well-known thermoelectric (TE) materials. Their TE characteristics emanate from a tunable electronic band structure achieved by adjusting the Bi/Sb ratio in the alloy. Their TE characteristics emanate from a tunable electronic band structure achieved by adjusting the Bi/Sb ratio in the alloy This material has attracted much attention in recent years on the recognition of a strong spin–orbit interaction (SOI) driven band crossing in the composition range of 0.03 < x < 0.22.3,4 For x ≈ 0.03, it acquires a Dirac-like metallic state, which changes to a 3D Weyl semimetal on application of a magnetic field, with signatures of the chiral anomaly in longitudinal magnetoresistance (LMR).. Electronic transport measurements on such crystals are characterized by a metal-like resistivity at low temperatures and the presence of weak Shubnikov–de Haas oscillations in the magnetic field dependence of longitudinal (ρxx) and Hall (ρxy) resistivity.8 These features of electronic transport have been attributed to spin–momentum locked surface states. We seek to find the existence of the planar Hall effect (PHE) and anisotropic magnetoresistance (AMR), which have been seen earlier in several non-magnetic topological insulators and the Dirac/Weyl family of semimetals.
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