@article{bc8dd84eebfb4e77b970f9ddc4470720,
title = "Role of the Heavy Metal's Crystal Phase in Oscillations of Perpendicular Magnetic Anisotropy and the Interfacial Dzyaloshinskii-Moriya Interaction in W/Co-Fe- B/MgO Films",
abstract = "The interfacial Dzyaloshinskii-Moriya interaction (IDMI) generally arises in {"}heavy-metal-ferromagnet{"} (HM-FM) heterostructures due the strong spin-orbit coupling in HMs and plays a crucial role in the nucleation of Dzyaloshinskii domain walls and Skyrmions that can be efficiently moved by spin-orbit torques. We study the IDMI in W/Co-Fe-B/MgO/Ta films with perpendicular magnetic anisotropy for different crystal structures and thicknesses of W layers treated by postsputtering annealing at 300 °C and 400 °C. We employ Brillouin light scattering spectroscopy to precisely measure the energy density and sign of the IDMI. We reveal two peaks associated with the IDMI: one for the amorphouslike phase of W, and another for α-W. The samples with pure β-W underlayers show the smallest values of IDMI. The sign of the IDMI is positive for all samples with the observed maximum effective and surface values of Deff=0.88 erg/cm2 and Ds=0.51×10-7 erg/cm, respectively. We report on the oscillating behavior of the IDMI as a function of thickness, which correlates with the surface anisotropy energy demonstrating common spin-orbit coupling and a robust dependence on the structural properties of the materials used. We ascribe the oscillations of the surface anisotropy and the IDMI mainly to the near inversely proportional dependence on the squared interatomic distance between the HM and FM atoms promoted by the thickness-driven crystal phase formation of W.",
author = "Kim, {Gyu Won} and Samardak, {Alexander S.} and Kim, {Yong Jin} and Cha, {In Ho} and Ognev, {Alexey V.} and Sadovnikov, {Alexandr V.} and Nikitov, {Sergey A.} and Kim, {Young Keun}",
note = "Funding Information: The authors are grateful to O. A. Tretiakov for the helpful discussion. We would also like to thank B.-H. Lee and A. Sarma from the Advanced Analysis Center, Korea Institute of Science and Technology for the help with Rietveld refinement. This work was supported in part by the Future Materials Discovery Program through the National Research Foundation of Korea, funded by the Ministry of Science and ICT (Grant No. 2015M3D1A1070465), by the Samsung Electronics{\textquoteright} University R&D program, by the Russian Foundation for Basic Research (Grants No. 18-52-53038 and No. 18-57-76001), by the Russian Ministry of Education and Science under the state task (Grants No. 3.5178.2017/8.9 and No. 3.4956.2017), by Act 211 of the Government of the Russian Federation (Contract No. 02.A03.21.0011), by Grant Council of the President of the Russian Federation (Scholarship No. SP-2819.2018.5 and Grant No. MK-3650.2018.9) and by the Brain Pool Program (Grant No. 172S-2-3-1928) through the Korean Federation of Science and Technology Societies (KOFST), funded by the Ministry of Science and ICT. Publisher Copyright: {\textcopyright} 2018 American Physical Society. Copyright: Copyright 2019 Elsevier B.V., All rights reserved.",
year = "2018",
month = jun,
day = "7",
doi = "10.1103/PhysRevApplied.9.064005",
language = "English",
volume = "9",
journal = "Physical Review Applied",
issn = "2331-7019",
publisher = "American Physical Society",
number = "6",
}