Superparamagnetic ground state of CoFeB/MgO magnetic tunnel junction with dual-barrier

Thanh Nga Tran, Tu Ngoc Lam, Chao Yao Yang, Wen Chin Lin, Po Wen Chen, Yuan-Chieh Tseng*

*Corresponding author for this work

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

CoFeB/MgO-based magnetic tunnel junctions (MTJs) have considerable potential in magnetic random access memory (MRAM), thanks to their tunable perpendicular magnetic anisotropy (PMA). We found significant reduction of dead-layer by inserting additional MgO into the MTJ structure. Interface, electronic and transport characterizations were utilized to approach the modified magnetic properties driven by the dual-MgO structure in this work. The dual-MgO structure appeared to hinder boron (B) diffusion into the metallic layer and prevent capping-layer (Ta) penetration across the interface. This suppressed the dead-layer effect and promoted overall magnetization despite PMA degradation. A robust BO x phase that formed within the dual-MgO structure presented a superparamagnetic ground state. In the single-MgO structure, any reduction in the thickness of the CoFeB promoted PMA, albeit at the cost of spin-polarization. The dual-MgO structure could restore spin-polarization by preferentially populating spin electrons into Fe/Co minority states. X-ray magnetic spectroscopy and anomalous Hall effect suggest that, the dual-MgO differs from the single-MgO with a favorable longitudinal polarized spin-channel. This makes the dual-MgO structure applicable to applications requiring in-plane rather than out-of-plane sensing.

Original languageEnglish
Pages (from-to)529-535
Number of pages7
JournalApplied Surface Science
Volume457
DOIs
StatePublished - 1 Nov 2018

Keywords

  • Magnetic random access memory
  • Magnetic tunnel junction
  • Perpendicular magnetic anisotropy
  • Spin-valve

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