Dual Referenced Composite Free Layer Design for Improved Switching Efficiency of Spin-Transfer Torque Random Access Memory

Roy Bell, Jiaxi Hu, R. H. Victora

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

A composite free layer spin-transfer torque random access memory (STT-RAM) cell is proposed for ultra-high density memory. The structure consists of three layers-a high anisotropy interior layer and two low anisotropy outer layers that assist the switching of the interior layer via exchange coupling. Efficiencies (kBT/μA) of 4.5 and 4.1 are achieved for the proposed structure with perpendicular and longitudinal anisotropies, respectively. An efficiency of 4.3 is obtained for the state-of-the-art single-layer dual-referenced structure with perpendicular anisotropy. Simulation of the conventional single-layer structure with perpendicular anisotropy yields an efficiency of 1.6. Therefore, the proposed structure with perpendicular anisotropy achieves an improvement of 5% and 181% relative to the state-of-the-art dual-referenced and conventional STT-RAM cells, respectively. Furthermore, use of low anisotropy assistive layers enables reduction of Gilbert damping and an increase of partial spin polarization within those low anisotropy layers-not feasible with single layer structures that require high anisotropy for thermal stability. This significantly increases perpendicular and longitudinal efficiencies to 8.5 and 6.8, respectively. Therefore, this augmented proposed structure with perpendicular anisotropy achieves an improvement of 99% and 446% relative to the state-of-the-art dual-referenced and conventional STT-RAM cells, respectively.

Original languageEnglish (US)
Article number7514225
Pages (from-to)1108-1111
Number of pages4
JournalIEEE Electron Device Letters
Volume37
Issue number9
DOIs
StatePublished - Sep 2016

Bibliographical note

Publisher Copyright:
© 2016 IEEE.

Keywords

  • STT-RAM
  • composite free layer
  • dual reference layer
  • spintronics

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