Experimental demonstration of the coexistence of spin Hall and Rashba effects inβ−tantalum/ferromagnetbilayers

We have measured the spin torques of beta-Tantalum / Co20Fe60B20 bilayers versus Ta thickness at room temperature using an FMR technique. The spin Hall coefficient was calculated both from the observed change in damping coefficient of the ferromagnet with Ta thickness, and from the ratio of the symmetric and anti-symmetric components of the FMR signal. Results from these two methods yielded values for the spin Hall coefficient of -0.090+/-0.005 and -0.11+/-0.01, respectively. We have also identified a significant out-of-plane spin torque originating from Ta, which is constant with Ta thickness. We ascribe this to an interface spin orbit coupling, or Rashba effect, due to the strength and constancy of the torque with Ta thickness. From fitting measured data to a model including interface spin orbit coupling, we have determined the spin diffusion length for beta-Tantalum to be ~2.5 nm.

[1]  J. Bass,et al.  Excitation of a magnetic multilayer by an electric current , 1998 .

[2]  Ralph,et al.  Current-driven magnetization reversal and spin-wave excitations in Co /Cu /Co pillars , 1999, Physical review letters.

[3]  A. Brataas,et al.  Spin pumping and magnetization dynamics in metallic multilayers , 2002, cond-mat/0208091.

[4]  M. Hosomi,et al.  A novel nonvolatile memory with spin torque transfer magnetization switching: spin-ram , 2005, IEEE InternationalElectron Devices Meeting, 2005. IEDM Technical Digest..

[5]  P. Kelly,et al.  Non-collinear magnetoelectronics , 2006, cond-mat/0602151.

[6]  William J. Gallagher,et al.  Development of the magnetic tunnel junction MRAM at IBM: From first junctions to a 16-Mb MRAM demonstrator chip , 2006, IBM J. Res. Dev..

[7]  Current-driven ferromagnetic resonance, mechanical torques, and rotary motion in magnetic nanostructures , 2006, cond-mat/0609258.

[8]  M. Venkatesan,et al.  Magnetic dead layers in sputtered Co40Fe40B20 films , 2008 .

[9]  D. Nikonov,et al.  Operation and Modeling of Semiconductor Spintronics Computing Devices , 2008 .

[10]  Mikhail I. Dyakonov.  Spin physics in semiconductors , 2008 .

[11]  Wolfgang Porod,et al.  Device and Architecture Outlook for Beyond CMOS Switches , 2010, Proceedings of the IEEE.

[12]  H. Oepen,et al.  Anisotropic interface magnetoresistance in Pt/Co/Pt sandwiches. , 2011, Physical review letters.

[13]  H. Kontani,et al.  Indication of intrinsic spin Hall effect in 4d and 5d transition metals , 2010, 1008.0158.

[14]  D. Ralph,et al.  Spin-torque ferromagnetic resonance induced by the spin Hall effect. , 2010, Physical review letters.

[15]  D. E. Nikonov,et al.  Uniform methodology for benchmarking beyond-CMOS logic devices , 2012, 2012 International Electron Devices Meeting.

[16]  D. Ralph,et al.  Spin transfer torque devices utilizing the giant spin Hall effect of tungsten , 2012, 1208.1711.

[17]  H. Nakayama,et al.  Interface induced inverse spin Hall effect in bismuth/permalloy bilayer , 2012 .

[18]  H. Noguchi,et al.  Progress of STT-MRAM technology and the effect on normally-off computing systems , 2012, 2012 International Electron Devices Meeting.

[19]  D. Ralph,et al.  Spin-Torque Switching with the Giant Spin Hall Effect of Tantalum , 2012, Science.

[20]  L. You,et al.  Possible route to low current, high speed, dynamic switching in a perpendicular anisotropy CoFeB-MgO junction using Spin Hall Effect of Ta , 2012, 2012 International Electron Devices Meeting.

[21]  Huaiwu Zhang,et al.  Observation of the nonlocal spin-orbital effective field , 2013, Nature Communications.

[22]  M. Stiles,et al.  Current induced torques and interfacial spin-orbit coupling: Semiclassical modeling , 2013, 1301.4513.

[23]  Dmitri E. Nikonov,et al.  Overview of Beyond-CMOS Devices and a Uniform Methodology for Their Benchmarking , 2013, Proceedings of the IEEE.

[24]  H. Ohno,et al.  Layer thickness dependence of the current-induced effective field vector in Ta|CoFeB|MgO. , 2012, Nature materials.

[25]  J. B. Youssef,et al.  Comparative measurements of inverse spin Hall effects and magnetoresistance in YIG/Pt and YIG/Ta , 2013, 1302.4416.

[26]  J. S. Lee,et al.  Spin-transfer torque generated by a topological insulator , 2014, Nature.

[27]  H. Ohno,et al.  Interface control of the magnetic chirality in CoFeB/MgO heterostructures with heavy-metal underlayers. , 2014, Nature communications.

[28]  Hyunsoo Yang,et al.  Angular and temperature dependence of current induced spin-orbit effective fields in Ta/CoFeB/MgO nanowires , 2014, Scientific reports.

[29]  Self-induced inverse spin Hall effect in permalloy at room temperature , 2013, 1301.3580.