Unusual perpendicular anisotropy in Co2TiSi films. (9th November 2018)

• Record Type: Journal Article
• Authors: Jin, Yunlong; Valloppilly, Shah; Kharel, Parashu; Pathak, Rohit; Kashyap, Arti; Skomski, Ralph; Sellmyer, D J
• Is Part Of: Journal of physics. Volume 52:Number 3(2019)
• Publication Date: 2018-11-09
• Subjects: perpendicular magnetic anisotropy -- Heusler alloy -- epitaxial thin films; Physics -- Periodicals; 530
• DOI: 10.1088/1361-6463/aae80f
• Languages: English
• ISSNs: 0022-3727

Abstract

Abstract: Thin films of Co2 TiSi on MgO are investigated experimentally and theoretically. The films were produced by magnetron sputtering on MgO(0 0 1) and have a thickness of about 100 nm. As bulk Co2 TiSi, 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 m −3 . 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, Co2 TiSi 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.