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Effect of off-stoichiometric composition on half-metallic character of Co2Fe(Ga,Ge) investigated using saturation magnetization and giant magnetoresistance effect
| Title: | Effect of off-stoichiometric composition on half-metallic character of Co2Fe(Ga,Ge) investigated using saturation magnetization and giant magnetoresistance effect |
| Authors: | Chikaso, Yuki Browse this author | | Inoue, Masaki Browse this author | | Tanimoto, Tessei Browse this author | | Kikuchi, Keita Browse this author | | Yamanouchi, Michihiko Browse this author →KAKEN DB | | Uemura, Tetsuya Browse this author →KAKEN DB | | Inubushi, Kazuumi Browse this author | | Nakada, Katsuyuki Browse this author | | Shinya, Hikari Browse this author | | Shirai, Masafumi Browse this author →KAKEN DB |
| Keywords: | Heusler alloy thin films | | half-metallic character | | giant magnetoresistance | | Co2Fe(Ga,Ge) |
| Issue Date: | 9-Jun-2022 |
| Publisher: | IOP Publishing |
| Journal Title: | Journal of Physics D : Applied Physics |
| Volume: | 55 |
| Issue: | 34 |
| Start Page: | 345003 |
| Publisher DOI: | 10.1088/1361-6463/ac73c1 |
| Abstract: | We investigated the Ge-composition (gamma) dependence of the saturation magnetization of Co2Fe(Ga, Ge) (CFGG) thin films and the magnetoresistance (MR) ratio of CFGG-based current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices together with first-principles calculations of the electronic states of CFGG. Theoretical calculations showed that spin polarization is highest at the stoichiometric composition gamma = 0.56 in Co2Fe1.03Ga0.41Ge (gamma) and that it decreases in off-stoichiometric CFGG, mainly due to the formation of Co-Fe antisites for Ge-deficient compositions and Fe-Co antisites for Ge-rich compositions, where Co-Fe (Fe-Co) indicates that Co (Fe) atoms replace the Fe (Co) sites. The saturation magnetic moment (mu (s)) per formula unit decreased monotonically as gamma increased from 0.24 to 1.54 in Co2Fe1.03Ga0.41Ge (gamma) . The mu (s) was closest to the Slater-Pauling value predicted for half-metallic CFGG at the stoichiometric composition gamma = 0.56, indicating that stoichiometric CFGG has a half-metallic nature. This is consistent with the result for the theoretical spin polarization. In contrast, the MR ratio of CFGG-based CPP-GMR devices increased monotonically as gamma increased from 0.24 to 1.10 and reached an MR ratio of 87.9% at the Ge-rich composition gamma = 1.10. Then, the MR ratio decreased rapidly as gamma increased from 1.10 to 1.48. Possible origins for the slight difference between the Ge composition at which the highest MR ratio was obtained (gamma = 1.10) and that at which the highest spin polarization was obtained (gamma = 0.56) are improved atomic arrangements in a Ge-rich CFGG film and the reduction of effective Ge composition due to Ge diffusion in the GMR stacks. |
| Rights: | This is the Accepted Manuscript version of an article accepted for publication in Journal of physics. D, Applied physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://doi.org/10.1088/1361-6463/ac73c1. |
| Type: | article (author version) |
| URI: | http://hdl.handle.net/2115/89806 |
| Appears in Collections: | 情報科学院・情報科学研究院 (Graduate School of Information Science and Technology / Faculty of Information Science and Technology) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
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Submitter: 植村 哲也
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