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Enhancement of magnetic coupling and magnetic anisotropy in MTJs with multiple CoFeB/MgO interfaces for high thermal stability

Authors :
K. Nishioka
H. Honjo
H. Naganuma
T. V. A. Nguyen
M. Yasuhira
S. Ikeda
T. Endoh
Source :
AIP Advances, Vol 11, Iss 2, Pp 025231-025231-5 (2021)
Publication Year :
2021
Publisher :
AIP Publishing LLC, 2021.

Abstract

Magnetic coupling between two CoFeB layers through the W insertion layer is important in the conventional double CoFeB/MgO interface, magnetic tunneling junctions (MTJs) (double-MTJs) with MgO/CoFeB/W/CoFeB/MgO free layer stack because it increases the effective magnetic volume of the free layer. The magnetic coupling energy constant per unit area, Jcpl, between two CoFeB layers through the W layer and the effective perpendicular magnetic anisotropy (PMA) energy constant per unit area, Kefft*, were investigated for conventional double-MTJs with various W insertion layer thicknesses. As the W layer thickness increased, Kefft* increased and Jcpl decreased. There exists a trade-off relationship between Jcpl and Kefft*. In conventional double-MTJs with a single W insertion layer, large values for Jcpl and Kefft* were difficult to obtain simultaneously. To improve this tradeoff, we employed a free layer stack with a thin ferromagnetic layer (ferromagnetic bridge layer: FBL) located in the W insertion layer. In the double-MTJs with FBL annealed at 400 °C, a large Jcpl value of 0.37 mJ/m2 was achieved while maintaining the maximum values of Kefft*. Accordingly, the MTJ with FBL provides an MTJ stack structure for obtaining high thermal stability.

Subjects

Subjects :
Physics
QC1-999

Details

Language :
English
ISSN :
21583226
Volume :
11
Issue :
2
Database :
Directory of Open Access Journals
Journal :
AIP Advances
Publication Type :
Academic Journal
Accession number :
edsdoj.b9ad07a83b8417b968f252dd0b545ec
Document Type :
article
Full Text :
https://doi.org/10.1063/9.0000048