Skip to content

Spin-orbit torque MRAMs: Materials, Physics, and Devices

Date: 2019-05-14
Time: 10:30
Venue: M253
Speaker: 朱礼军 博士

Cornell University, USA

报告人简介: Dr. Lijun Zhu received his B.S. degree in 2009 in Beijing Normal University and Ph.D. degree in 2014 in Institute of Semiconductors, Chinese Academy of Sciences. His PhD thesis topic was “Growth, magnetism and transport of materials with giant perpendicular magnetic anisotropy”. From Jun. 2014-Feb. 2016, he worked on ferromagnetic resonance and pump-probe MOKE studies as a postdoc at the Martin-Luther University in Halle, Germany. Since March 2016 Lijun has been conducting postdoctoral research with Prof. Robert Buhrman and Prof. Daniel Ralph at Cornell University, USA. His current research focuses on developing new strong spin Hall materials and advancing the understanding of the interfacial spin transport for achieving energy-efficient spin-orbit-torque-switching of MRAM devices.

报告摘要:Spin-orbit torque MRAMs are considered as next-generation non-volatile memory solution due to the potential of ultrafast energy-efficient write and unlimited endurance. However, the energy efficiency of the present spin-torque operations are still limited because of the low spin Hall ratio and/or high resistivity of the spin Hall materials and low efficiency of interfacial spin transport. This talk will first report recent achievements of very compelling spin Hall metals with highly efficient spin current generation and relatively low resistivity at the same time [1-3]. This talk will also show that spin pumping is a minor effect in determining the thickness dependence of magnetic damping, neglecting which will result in unphysical “giant” apparent effective spin-mixing conductance ( ), the key factor determining the spin transparency of a HM/FM interface, and hence a considerable underestimation of both the spin Hall ratio and the spin Hall conductivity in inverse/direct spin Hall experiments [4]. This talk will also report conclusive experimental evidence that interfacial spin-orbit coupling degrades the SOTs exerted on the FM layer by the spin currents generated in the HM [5], while interfacial intermixing at a Pt/Co interface can increase interfacial spin transparency [6], by approximately 30 %. Finally, ultrafast energy-efficient spin-torque MRAMs devices will be also demonstrated [3].

[1] L. Zhu et al., Phys. Rev. Appl. 10, 031001 (2018). (Letter, Editors’ suggestion)
[2] L. Zhu et al., Adv. Funct. Mater. 29, 1805822 (2019).
[3] L. Zhu et al., Phys. Rev. Appl. (2019)(Letter, in press). arXiv:1904.07800
[4] L. Zhu et al., Phys. Rev. Lett. (in press). arXiv:1905.01577
[5] L. Zhu et al., Phys. Rev. Lett. 122, 077201 (2019).
[6] L. Zhu et al., Phys. Rev. B (R)(2019)(in press). arXiv:1904.05455

联系人:蔡建旺(9094)