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Title: Time-domain detection of current controlled magnetization damping in Pt/Ni{sub 81}Fe{sub 19} bilayer and determination of Pt spin Hall angle

Abstract

The effect of spin torque from the spin Hall effect in Pt/Ni{sub 81}Fe{sub 19} rectangular bilayer film was investigated using time-resolved magneto-optical Kerr microscopy. Current flow through the stack resulted in a linear variation of effective damping up to ±7%, attributed to spin current injection from the Pt into the Ni{sub 81}Fe{sub 19}. The spin Hall angle of Pt was estimated as 0.11 ± 0.03. The modulation of the damping depended on the angle between the current and the bias magnetic field. These results demonstrate the importance of optical detection of precessional magnetization dynamics for studying spin transfer torque due to spin Hall effect.

Authors:
; ; ;  [1]; ; ; ;  [2]
  1. Thematic Unit of Excellence on Nanodevice Technology, Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Kolkata 700098 (India)
  2. Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom)
Publication Date:
OSTI Identifier:
22303524
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 11; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CURRENTS; DETECTION; FILMS; HALL EFFECT; INJECTION; IRON ALLOYS; KERR EFFECT; LAYERS; MAGNETIC FIELDS; MAGNETIZATION; MAGNETO-OPTICAL EFFECTS; MODULATION; NICKEL ALLOYS; PLATINUM; SPIN; TIME RESOLUTION; TORQUE

Citation Formats

Ganguly, A., Haldar, A., Sinha, J., Barman, A., E-mail: abarman@bose.res.in, E-mail: del.atkinson@durham.ac.uk, Rowan-Robinson, R. M., Jaiswal, S., Hindmarch, A. T., and Atkinson, D. A., E-mail: abarman@bose.res.in, E-mail: del.atkinson@durham.ac.uk. Time-domain detection of current controlled magnetization damping in Pt/Ni{sub 81}Fe{sub 19} bilayer and determination of Pt spin Hall angle. United States: N. p., 2014. Web. doi:10.1063/1.4896277.
Ganguly, A., Haldar, A., Sinha, J., Barman, A., E-mail: abarman@bose.res.in, E-mail: del.atkinson@durham.ac.uk, Rowan-Robinson, R. M., Jaiswal, S., Hindmarch, A. T., & Atkinson, D. A., E-mail: abarman@bose.res.in, E-mail: del.atkinson@durham.ac.uk. Time-domain detection of current controlled magnetization damping in Pt/Ni{sub 81}Fe{sub 19} bilayer and determination of Pt spin Hall angle. United States. doi:10.1063/1.4896277.
Ganguly, A., Haldar, A., Sinha, J., Barman, A., E-mail: abarman@bose.res.in, E-mail: del.atkinson@durham.ac.uk, Rowan-Robinson, R. M., Jaiswal, S., Hindmarch, A. T., and Atkinson, D. A., E-mail: abarman@bose.res.in, E-mail: del.atkinson@durham.ac.uk. Mon . "Time-domain detection of current controlled magnetization damping in Pt/Ni{sub 81}Fe{sub 19} bilayer and determination of Pt spin Hall angle". United States. doi:10.1063/1.4896277.
@article{osti_22303524,
title = {Time-domain detection of current controlled magnetization damping in Pt/Ni{sub 81}Fe{sub 19} bilayer and determination of Pt spin Hall angle},
author = {Ganguly, A. and Haldar, A. and Sinha, J. and Barman, A., E-mail: abarman@bose.res.in, E-mail: del.atkinson@durham.ac.uk and Rowan-Robinson, R. M. and Jaiswal, S. and Hindmarch, A. T. and Atkinson, D. A., E-mail: abarman@bose.res.in, E-mail: del.atkinson@durham.ac.uk},
abstractNote = {The effect of spin torque from the spin Hall effect in Pt/Ni{sub 81}Fe{sub 19} rectangular bilayer film was investigated using time-resolved magneto-optical Kerr microscopy. Current flow through the stack resulted in a linear variation of effective damping up to ±7%, attributed to spin current injection from the Pt into the Ni{sub 81}Fe{sub 19}. The spin Hall angle of Pt was estimated as 0.11 ± 0.03. The modulation of the damping depended on the angle between the current and the bias magnetic field. These results demonstrate the importance of optical detection of precessional magnetization dynamics for studying spin transfer torque due to spin Hall effect.},
doi = {10.1063/1.4896277},
journal = {Applied Physics Letters},
number = 11,
volume = 105,
place = {United States},
year = {Mon Sep 15 00:00:00 EDT 2014},
month = {Mon Sep 15 00:00:00 EDT 2014}
}
  • The rise and damping of spin excitations in three Ni{sub 81}Fe{sub 19} films of thickness 50, 500, and 5000 Aa have been studied with an optical pump{endash}probe technique in which the sample is pumped with an optically triggered magnetic field pulse. The motion of the magnetization was described by the uniform mode solution of the Landau{endash}Lifshitz{endash}Gilbert equation. The rise time of the pulsed field within the film was smallest in the 50 Aa sample and was generally greater when the pulsed field was perpendicular to the film plane. The damping constant was smallest in the 500 Aa sample. The variationsmore » in the rise time and damping are attributed to the presence of eddy currents and structural disorder in the films. Under certain excitation conditions a second mode was observed in the 5000 Aa sample which we believe to be a magnetostatic surface mode. {copyright} 2001 American Institute of Physics.« less
  • The layer magnetization, the saturation magnetization as well as the magnetic anisotropy, and damping behavior of 20 nm thick Ni{sub 81}Fe{sub 19} films have been modified by 30 keV Ni ion implantation with fluences up to 1x10{sup 16} Ni/cm{sup 2} ({approx_equal}5 at. %). With increasing ion fluence a magnetic dead layer of increasing thickness is formed which leads to a reduction of the total magnetization. In addition, the saturation magnetization of the residual ferromagnetic film decreases due to, both, a shift in stoichiometry and radiation damage. Accordingly a reduction of the magnetic anisotropy and a strong enhancement of the magneticmore » damping parameter are observed. Moreover, ion implantation in an applied magnetic field allows the setting of the uniaxial anisotropy direction irrespective of its original orientation. Static and dynamic magnetic properties of Ni{sub 81}Fe{sub 19} films can be tailored over a wide range after film deposition.« less
  • Pure magnetic patterning by means of ion-beam irradiation of magnetic thin films and multilayers often results from a postdeposition local modification of the interface structure with only minor effects on the film topography. In the study presented here a 60 keV fine-focused Co ion beam was used to change the coupling in a Ni{sub 81}Fe{sub 19}/Ru/Co{sub 90}Fe{sub 10} structure from antiferromagnetic to ferromagnetic on a micron scale. Thereby an artificial structure with locally varying interlayer exchange coupling and therefore magnetization alignment is produced. High-resolution full-field x-ray microscopy is used to determine the magnetic domain configuration during the magnetization reversal processmore » locally and layer resolved due to the element-specific contrast in circular x-ray dichroism. In the magnetically patterned structure there is, in addition to the locally varying interlayer exchange coupling across the Ru layer, also the direct exchange coupling within each ferromagnetic layer present. Therefore the magnetization reversal behavior of the irradiated stripes is largely influenced by the surrounding magnetic film.« less
  • Spin pumping has been studied within Ta / Ag / Ni 81Fe 19 (0–5 nm) / Ag (6 nm) / Co 2MnGe (5 nm) / Ag / Ta large-area spin-valve structures, and the transverse spin current absorption of Ni 81Fe 19 sink layers of different thicknesses has been explored. In some circumstances, the spin current absorption can be inferred from the modification of the Co 2MnGe source layer damping in vector network analyzer ferromagnetic resonance (VNA-FMR) experiments. However, the spin current absorption is more accurately determined from element-specific phase-resolved x-ray ferromagnetic resonance (XFMR) measurements that directly probe the spin transfermore » torque (STT) acting on the sink layer at the source layer resonance. Comparison with a macrospin model allows the real part of the effective spin mixing conductance to be extracted. We find that spin current absorption in the outer Ta layers has a significant impact, while sink layers with thicknesses of less than 0.6 nm are found to be discontinuous and superparamagnetic at room temperature, and lead to a noticeable increase of the source layer damping. For the thickest 5-nm sink layer, increased spin current absorption is found to coincide with a reduction of the zero frequency FMR linewidth that we attribute to improved interface quality. Furthermore, this study shows that the transverse spin current absorption does not follow a universal dependence upon sink layer thickness but instead the structural quality of the sink layer plays a crucial role.« less