Dependence of spin pumping and spin transfer torque upon Ni81Fe19 thickness in Ta/Ag/Ni81

Abstract

Spin pumping has been studied within Ta/Ag/Ni 81 Fe 19 (0-5 nm)/Ag(6 nm)/Co 2 MnGe(5 nm)/Ag/Ta large-area spin valve structures, and the transverse spin current absorption of Ni 81 Fe 19 sink layers of different thickness has been explored. In some circumstances the spin current absorption can be inferred from the modification of the Co 2 MnGe source layer damping in vector network analyser 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 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 thickness 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 linewidth 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.

Nonreciprocal spin pumping damping in asymmetric magnetic trilayers

“…We focus our discussion on the spin mixing conductance of layer i, (g ↑↓ i ) related to the dimensionless spin pumping parameter η ij . In particular it has been shown that the real part of g ↑↓ i relates to η ij as [39] R(…”

Experimental realization of linearly polarized x-ray detected ferromagnetic resonance

“…However, experimental techniques that offer these capabilities are lacking. X-ray detected ferromagnetic resonance (XFMR) with circularly polarized x-rays, i.e., dynamic x-ray magnetic circular dichroism (XMCD) [11][12][13], has proven an indispensable tool in the investigations of spin dynamics in magnetic multilayers [7,8,[14][15][16][17][18][19][20][21][22][23][24][25][26]. By combining the capabilities of ferromagnetic resonance (FMR) and x-ray absorption spectroscopy as the underlying characterization mechanism, dynamic XMCD can probe magnetic precessions with element specificity, valence state sensitivity, and phase resolution.…”

“…By combining the capabilities of ferromagnetic resonance (FMR) and x-ray absorption spectroscopy as the underlying characterization mechanism, dynamic XMCD can probe magnetic precessions with element specificity, valence state sensitivity, and phase resolution. XFMR has enabled the determination of effective spin mixing conductance of a spin valve with multiple spin sink layers [26], resolving interlayer anisotropic Gilbert damping effects in magnetic source and sink layers coupled by spin pumping [24], and the detection of coherent AC spin current propagation through antiferromagnetic CoO [7] and NiO [8]. Analogous to its static counterpart, dynamic XMCD is sensitive to ferromagnetic order and probes the net vector sum of magnetic moments associated with a certain element or ion.…”

Spin Pumping in Asymmetric Fe50Pt50/Cu/Fe20Ni80 Trilayer Structure

“…However, for asymmetric system similar to the present case, where FM1 and FM2 are designed with different intrinsic parameters (uniaxial and cubic anisotropy, shape anisotropy, saturation magnetization), spin pumping is to be analyzed as a nonreciprocal process with dissimilar values of and for the different material interface on each side of the insertion layer . However, a simplified approximation that is also debated in the literature . In this comprehensive study, we performed field‐sweep broadband ferromagnetic resonance (FMR) measurements using vector network analyzer (VNA) to analyze spin‐pumping in soft magnetic and asymmetric Fe 50 Pt 50 /Cu/Fe 20 Ni 80 trilayer structure.…”

“…Following the practice for other frequencies, the extracted values are plotted as a function of for Fe 50 Pt 50 and Fe 20 Ni 80 in Figure c,d respectively. From the slope of anticipated linear dependence, we calculated the effective damping parameter using , where the reference value of = 29.5 GHz T −1 and = 29.5 GHz T −1 is considered from literature . Noticeable enhancement in damping parameter = 0.015 ± 0.001 and 0.031 ± 0.001 is obtained for Fe 20 Ni 80 and Fe 50 Pt 50 , respectively, in multilayer sample attributed to spin‐pumping effect, while uncapped samples Si/Fe 20 Ni 80 and Si/Fe 50 Pt 50 exhibited smaller values of α °, to be 0.0059 ± 0.0003 and 0.0228 ± 0.0006, respectively .…”