Zhanjie Li

Publications (2)3.84 Total impact

• Article: Spin transfer switching in dual MgO magnetic tunnel junctions

  Zhitao Diao, Alex Panchula, Yunfei Ding, Mahendra Pakala, Shengyuan Wang, Zhanjie Li, Dmytro Apalkov, Hideyasu Nagai, Alexander Driskill-Smith, Lien-Chang Wang, Eugene Chen, Yiming Huai
  [show abstract] [hide abstract]
  ABSTRACT: Dual magnetic tunnel junction (MTJ) structures consisting of two MgO insulating barriers of different resistances, two pinned reference layers aligned antiparallel to one another, and a free layer embedded between the two insulating barriers have been developed. The electron transport and spin dependent resistances in the dual MTJ structures are accounted for by sequential tunneling with some spin-flip relaxation in the central electrode (the free layer). With a tunneling magnetoresistance ratio of 70%, a switching current density Jc (at 30 ms) of 0.52 MA/cm2 is obtained, corresponding to an intrinsic value of Jc0 (at 1 ns) of 1.0 MA/cm2. This value of Jc0 is 2–3 times smaller than that of a single MgO insulating barrier MTJ structure and results from improvements in the spin-transfer torque efficiency. The asymmetry between JcAP→P and JcP→AP is significantly improved, which widens the read-write margin for memory device design. In addition, the experimental results show that the switching current density can be further reduced when an external field is applied along the hard axis of the free layer.
  Applied Physics Letters 03/2007; 90(13):132508-132508-3. · 3.84 Impact Factor
• Source

  Available from: technion.ac.il

  Article: Spin-transfer torque switching in magnetic tunnel junctions and spin-transfer torque random access memory

  Zhitao Diao, Zhanjie Li, Shengyuang Wang, Yunfei Ding, Alex Panchula, Eugene Chen, Lien-Chang Wang, Yiming Huai
  [show abstract] [hide abstract]
  ABSTRACT: We present experimental and numerical results of current-driven magnetization switching in magnetic tunnel junctions. The experiments show that, for MgO-based magnetic tunnelling junctions, the tunnelling magnetoresistance ratio is as large as 155% and the intrinsic switching current density is as low as 1.1 × 10 6 A cm −2 . The thermal effect and current pulse width on spin-transfer magnetization switching are explored based on the analytical and numerical calculations. Three distinct switching modes, thermal activation, dynamic reversal, and precessional process, are identified within the experimental parameter space. The switching current distribution, write error, and read disturb are discussed based on device design considerations. The challenges and requirements for the successful application of spin-transfer torque as the write scheme in random access memory are addressed.
  J. Phys.: Condens. Matter. 01/2007; 19:165209-13.