Ultra-Low Write Energy Composite Free Layer Spin-Orbit Torque MRAM

Wei Heng Hsu, Roy Bell, Randall H Victora

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


A highly efficient exchange-coupled free-layer spin-orbit torque (SOT) magnetic random access memory cell is proposed for ultra-high-density memory. By exploiting typically unrealized benefits of SOT - in particular, its compatibility with low-damping magnetic insulators and the energy efficiencies associated with exchange coupling of hard/soft composite structures - a write energy of 18 aJ/bit for 1 ns switching is achieved. Furthermore, high magnetocrystalline anisotropy materials such as L10-FePt or L10-FePd are employed not only to facilitate achievement of ultra-high-density memory but also to allow for reduction of heavy metal layer volume and a reduction in write energy not seen in previous CoFeB-based cells. This energy is within a factor 72 of the theoretical limit of 60k BT. It also represents a factor of >500 improvement relative to state-of-the-art DDR4 DRAM cells.

Original languageEnglish (US)
Article number8403885
JournalIEEE Transactions on Magnetics
Issue number11
StatePublished - Nov 2018


  • Composite free layer
  • magnetic insulator (MI)
  • micromagnetic simulation
  • spin-orbit torque (SOT)

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