Effect of sink layer thickness on damping in CoMnGe (5 nm) / Ag (6 nm) / NiFe (x nm) spin valves

Authors: Robert Alexander James Valkass (University of Exeter) , Leigh R. Shelford (University of Exeter) , Chris J. Durrant (University of Exeter) , Adriana Figueroa (University of Exeter) , Alex A. Baker (University of Exeter) , Padraic Shafer (University of Exeter) , Elke Arenholz (University of Exeter) , Jeffrey R. Childress (University of Exeter) , Jordan A. Katine (University of Exeter) , Gerrit Van Der Laan (University of Exeter) , Robert Hicken (University of Exeter)
Co-authored by industrial partner: No

Type: Poster

State: Published (Approved)
Published: April 2016
Diamond Proposal Number(s): 8782 , 11585 , 13063

Open Access Open Access

Abstract: In spin valve structures the damping of a ferromagnetic layer driven at resonance can be modified by the transfer of spin angular momentum into a ‘sink’ ferromagnetic layer. This effect, known as spin pumping, is interface dominated and expected to increase with increasing sink layer thickness up to a saturation absorption depth, previously reported to be 1.2 nm regardless of the sink layer’s composition [1]. Using vector network analyser ferromagnetic resonance (VNA-FMR), we have studied the variation in damping as a function of sink layer thickness in a series of CoMnGe (5 nm) / Ag (6 nm) / NiFe (x nm) spin valves. These measurements show only small variations in the CoMnGe Gilbert damping parameter for x ≤ 1.8 nm, although damping is observed to increase at x = 0.3 and 0.6 nm. Element-resolved x-ray detected ferromagnetic resonance (XFMR) [2] measurements confirm spin transfer torque due to spin pumping as the origin of the damping for x = 1.5 and 1.8 nm, with both thicknesses having the same effective spin mixing conductance, supporting the findings of Ghosh et al [1]. For thicker sink layers the source and sink FMR fields are seen to coincide, hampering the identification of spin pumping. [1] A Ghosh, et al. Physical Review Letters 109, 127202 (2012) [2] M Marcham, et al. Physical Review B 87, 180403 (2013)

Subject Areas: Materials, Physics

Instruments: I06-Nanoscience , I10-Beamline for Advanced Dichroism

Other Facilities: Advanced Light Source