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Tunable PMA and Interfacial Microstructure Induced by a Hf(HfO 2 ) Interfacial Spacer in MTJs with Two MgO Layers
Author(s) -
Li Minghua,
Wang Shuanghai,
Zhang Shijie,
Fang Shuai,
Cao Xingzhong,
Wang Baoyi,
Zhang Peng,
Yu Guanghua
Publication year - 2019
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201900089
Subject(s) - materials science , microstructure , amorphous solid , annealing (glass) , x ray photoelectron spectroscopy , oxide , transmission electron microscopy , ferromagnetism , metal , layer (electronics) , crystallography , nanotechnology , composite material , chemical engineering , metallurgy , condensed matter physics , chemistry , physics , engineering
The insertion of a metal (metal oxide) layer in a ferromagnetic layer is highly effective for tailoring the interfacial microstructures of magnetic multilayers and consequently their physical, chemical, and magnetic properties. In this study, the authors add Hf (HfO 2 ) spacer layers to magnetic tunnel junctions (MTJs) with two MgO layers to ensure the perpendicular magnetic anisotropy (PMA) of the films after annealing at 375 °C. High‐resolution transmission electron microscopy shows that the MgO and Ta layers are partially crystallized, while the CoFeB layers are predominantly amorphous. The different Ta, MgO, and CoFeB layers can be easily distinguished by energy‐dispersive X‐ray spectroscopy. X‐ray photoelectron spectroscopy indicates that some HfO 2 is formed when the film is deposited, and more HfO 2 is formed during annealing. More Fe and Co oxides are also formed as oxygen reduced from BO x and MgO combines with Fe and Co in the CoFeB layer, which strengthens the PMA. The results indicate that the insertion of a metal (metal oxide) layer is an effective way to improve the magnetic properties of MTJs.