Influence of HfO2 interlayers on magnetocrystalline anisotropy in Fe |MgO |Fe magnetic tunnel junction: First-principles investigation

Perpendicular magnetic anisotropy (PMA) is important for MgO based magnetic tunnel junction and magnetic random access memory to be integrated on a large scale due to high thermal stability and low critical switching current. Here, we applied the density functional theory to study the effect of HfO...

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Bibliographic Details
Published in:Journal of applied physics 2019-06, Vol.125 (23)
Main Authors: Chen, W. Z., Zhang, J., Yang, B. S., Jiang, L. N., Yu, T., Han, X. F.
Format: Article
Language:English
Subjects:
Anisotropy
Applied physics
Density functional theory
Dependence
First principles
Hafnium oxide
Interlayers
Large scale integration
Magnesium oxide
Magnetic anisotropy
Perturbation theory
Random access memory
Thermal stability
Tunnel junctions
Unit cell
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Summary:Perpendicular magnetic anisotropy (PMA) is important for MgO based magnetic tunnel junction and magnetic random access memory to be integrated on a large scale due to high thermal stability and low critical switching current. Here, we applied the density functional theory to study the effect of HfO 2 inserting layers on PMA of Fe |MgO |Fe tunnel junction. It was found that the magnetocrystalline anisotropy (MCA) of the junction for 5 layers Fe electrode was up to 1.95 mJ/m 2 with one unit cell HfO 2 interlayer, while it was 1.72 mJ/m 2 without the interlayer. More importantly, analyzed by the layer and orbital-resolved MCA based on the second-order perturbation theory, MCA characters and the underlying mechanism of PMA become very different after inserting HfO 2. The remarkable difference is the MCA contribution of the second interfacial Fe layers, which is about 0.4 mJ/m 2 for Fe |MgO |Fe junctions, while it was larger than 0.7 mJ/m 2 for Fe |HfO 2 |MgO |HfO 2 |Fe junctions. Furthermore, Fe-d z 2 and O-p z hybridization plays a crucial role in MCA contribution from the first interfacial Fe layers since the interfacial Fe–O bond length reduces from 2.20 Å to 1.77 Å with inserting HfO 2 layers. Besides, the reduction in Fe–O bond length can redistribute the orbital-resolved electrons of the second and third closest Fe layer to the interface to enhance their absolute values of MCA contributions, which results in the strong dependence of MCA on Fe thickness.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.5095654