Research Papers in Physics and Astronomy



Yunlong Jin,

Date of this Version



Published in Journal of Physics D: Applied Physics 52 (2019), 035001

doi 10.1088/1361-6463/aae80f


Copyright © 2018 IOP Publishing Ltd. Used by permission.


Thin films of Co2TiSi on MgO are investigated experimentally and theoretically. The films were produced by magnetron sputtering on MgO(001) and have a thickness of about 100 nm. As bulk Co2TiSi, they crystallize in the normal cubic Heusler (L21) structure, but the films are slightly distorted (c/a = 1.0014) and contain some antisite disorder. The films exhibit a robust perpendicular anisotropy of 0.5 MJ m3. This result is surprising for several reasons. First, surface and interface anisotropies are too small to explain perpendicular anisotropy in such rather thick films. Second, Co2TiSi has a substantial magnetization and crystallizes in a cubic Heusler structure, so that conventional wisdom predicts a preferential magnetization direction in the film plane rather than perpendicular. Third, the lattice strain of 0.14% is unable to account for the perpendicular anisotropy. We explain the perpendicular anisotropy as a quasicubic symmetry breaking chemical-ordering effect promoted by the substrate.