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MMM 2022

November 07, 2022

Minneapolis, United States

Anomalous Hall Effect and Anisotropic Magnetoresistance Effect in Co2(Ti1 xVx)Si Heusler Alloy Single Crystal Films

Recently, Co2TiSi Heusler alloy is theoretically predicted that is one of the ferromagnetic Weyl semimetal (WSM) candidates, and also the half-metal (1, 2, 3), which has potential for both a large anomalous Hall effect (AHE) and a large spin polarization. It is also expected that the anomalous Hall effect can be enhanced by customizing Co2(Ti1-xVx)Si due to the Fermi level shift (4, 5). In this research, we optimized the fabrication conditions for producing Co2(Ti1-xVx)Si thin films, and investigated their AHE and anisotropic magnetoresistance (AMR) effect to discuss the electronic structure in Co2(Ti1-xVx)Si. The UHV magnetron co-sputtering method was used for the preparation of thin films using Co2TiSi and Co2VSi targets. The structure of the sample was MgO (001) sub. / Co2(Ti1-xVx)Si (50 nm) / Ta (5 nm), and the doping amount of x was changed. We characterized the crystal structure, magnetic properties, AHE and AMR effect by XRD, SQUID, and PPMS, respectively. High quality L21 ordered single crystal films (SL21 ≈ 70%) were successfully fabricated by applying adequate annealing process. Fig. 1 shows doping value x dependence of anomalous Hall angle (AHA), measured at 10 K. AHA of Co2(Ti1-xVx)Si sample films enhanced by V doping, and the highest AHA was observed near 3% at x = 0.31. Fig. 2 shows measurement temperature dependence of AMR radio when the electric current flowed in the Co2(Ti1-xVx)Si 110 and 100 directions. The magnitude of AMR ratio increases with decreasing temperature for both directions, but the sign is positive for 110 and negative for 100 direction, respectively. The s-d scattering theory of AMR (6) suggests that d-orbitals of majority spin electron are split by crystal field and the density of states of ε- and γ-orbitals are well different at the Fermi level. The change of magnitude of AMR for 100 direction implies that the Fermi level tuning was realized by V doping into the Co2TiSi Heusler alloy thin films. This research was conducted by participating in the GP-Spin and JST's SPRING program, Tohoku University, and supported by CSIS Organization for Advanced Studies and the CSRN.

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(4) J. Zou, Z. He, and G. Xu, Npj Computational Materials, 5(1) (2019).
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(6) S. Kokado and M. Tsunoda, J. Phys. Soc. Jpn. 88, 034706 (2019).

Next from MMM 2022

Enhanced multiferroic properties in Bi0.9H0.1FeO3 polycrystalline films (H = heavy rare earth elements)

Enhanced multiferroic properties in Bi0.9H0.1FeO3 polycrystalline films (H = heavy rare earth elements)

MMM 2022

T.K. Lin and 5 other authors

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