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In this study, we explored the HEO thin films with a rock-salt-like structure of LiTiMgAlGaO for perpendicular magnetic anisotropy (PMA), which is induced at an interface with the CoFeB ferromagnet. The atomically homogeneous cation distributions in the 10-20 nm thick LiTiMgAlGaO films were achieved by atomic sputtering lamination on a MgO(001) single crystal substrate. The films were grown with a highly (001)-oriented epitaxial growth and have an atomically flat surface with an average roughness of 0.07 nm. We observed perpendicular magnetization of CoFeB on the LiTiMgAlGaO layer after 250-350C post-annealing, revealing that introduction of significantly large PMA at HEO/ferromagnet interfaces. A large interface PMA energy of up to ~0.8 erg/cm2 at the interface was observed due to the achievement of structurally stable epitaxial layers with high crystallinity and sharp interfacial flatness of L5O and CFB interfaces. We also demonstrated that a tunnel magnetoresistance (TMR) ratio of up to 84% at room temperature in epitaxial Fe/L5O/Fe(001) magnetic tunnel junctions (MTJs) with ultrathin MgO insertions at the L5O interfaces, indicating that the spin-dependent coherent tunneling mechanism is also observed in HEO-based MTJs. In addition, the L5O barrier exhibits low barrier heights less than 1 eV due to the bandgap reduction caused by the five cations. Our results of the high interface PMA energy, the relatively large TMR ratio, and the low barrier height show that the HEO materials can be a promising material family of ultra-thin barriers of MTJs for the next generation of high-density spintronic devices such as ultra-high-density memory and spin artificial intelligence devices.

権利情報:

• Creative Commons BY Attribution 4.0 International
  

キーワード: High entropy oxides, Epitaxial growth, Spintronics, Perpendicular magnetization, Tunnel magnetoresistance

刊行年月日: 2025-07-05

出版者: Elsevier BV

掲載誌:

• Materials Today (ISSN: 13697021) vol. 88 p. 12-23

研究助成金:

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.1016/j.mattod.2025.06.025

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更新時刻: 2025-09-02 16:30:19 +0900

MDRでの公開時刻: 2025-09-02 12:25:00 +0900