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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