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Dependence of spin pumping and spin transfer torque upon Ni81Fe19 thickness in Ta/Ag/Ni81Fe19/Ag/Co2MnGe/Ag/Ta spin-valve structures

DOI: 10.1103/PhysRevB.96.144421 DOI Help

Authors: C. J. Durrant (University of Exeter) , L. R. Shelford (University of Exeter) , R. A. J. Valkass (University of Exeter) , R. J. Hicken (University of Exeter) , A. I. Figueroa (Diamond Light Source) , A. A. Baker (Diamond Light Source) , G. Van Der Laan (Diamond Light Source) , L. B. Duffy (University of Oxford) , P. Shafer (Advanced Light Source) , C. Klewe (University of Bielefeld) , E. Arenholz (Advanced Light Source) , S. A. Cavill (University of York) , J. R. Childress (HGST) , J. A. Katine (HGST)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 96 , PAGES 144421

State: Published (Approved)
Published: October 2017
Diamond Proposal Number(s): 8782 , 11585

Abstract: Spin pumping has been studied within Ta / Ag / Ni81Fe19 (0–5 nm) / Ag (6 nm) / Co2MnGe (5 nm) / Ag / Ta large-area spin-valve structures, and the transverse spin current absorption of Ni81Fe19 sink layers of different thicknesses has been explored. In some circumstances, the spin current absorption can be inferred from the modification of the Co2MnGe source layer damping in vector network analyzer ferromagnetic resonance (VNAFMR) 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 transfer 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 super-paramagnetic 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 line width that we attribute to improved interface quality. 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.

Journal Keywords: spintronics, magnetism

Subject Areas: Physics, Materials, Technique Development

Diamond Offline Facilities: Magnetic Spectroscopy Lab
Instruments: I06-Nanoscience , I10-Beamline for Advanced Dichroism

Other Facilities: ALS Berkeley