Spin-Pumping-Induced Inverse Spin Hall Effect in Nb/Ni80Fe20 Bilayers and its Strong Decay Across the Superconducting Transition Temperature

Abstract

We quantify the spin Hall angle θ SH and spin-diffusion length l sd of Nb from inverse spin Hall effect (ISHE) measurements in Nb/Ni 80 Fe 20 bilayers under ferromagnetic resonance. By varying the Nb thickness t Nb and comparing to a Ni 80 Fe 20 /Pt reference sample, room temperature values of θ SH and l sd for Nb are estimated to be approximately −0.001 and 30 nm, respectively. We also investigate the ISHE as a function of temperature T for different t Nb . Above the superconducting transition temperature T c of Nb, a clear t Nb -dependent T evolution of the ISHE is observed whereas below T c , the ISHE voltage drops rapidly and is below the sensitivity of our measurement setup at a lower T. This suggests the strong decay of the quasiparticle (QP) charge-imbalance relaxation length across T c , as supported by an additional investigation of the ISHE in a different sample geometry along with model calculation. Our finding suggests careful consideration should be made when developing superconductor spin Hall devices that intend to utilize QP-mediated spin-to-charge interconversion.

Extrinsic spin-charge coupling in diffusive superconducting systems

“…It is worth mentioning that θ and κ defined by Eqs. (65) and (66) are not the total spin Hall angle and the spin swapping coefficient. In Eq.…”

Upper Frequency Limits for Vortex Guiding and Ratchet Effects

“…Recently, the microwave response of systems composed of superconducting and ferromagnetic nanostructures has attracted especial attention [48][49][50][51][52][53][54][55]. Due to the antagonistic spin ordering [56] the interplay of superconductivity and ferromagnetism leads to competing ground states, affecting the spin transport [52] and the dynamics of magnetic moment excitations [48][49][50][51][52][53][54][55].…”

“…Recently, the microwave response of systems composed of superconducting and ferromagnetic nanostructures has attracted especial attention [48][49][50][51][52][53][54][55]. Due to the antagonistic spin ordering [56] the interplay of superconductivity and ferromagnetism leads to competing ground states, affecting the spin transport [52] and the dynamics of magnetic moment excitations [48][49][50][51][52][53][54][55]. Exemplary phenomena emerging at microwave frequencies include the generation of superconducting pure spin currents [51], shortening of the quasiparticle charge-imbalance relaxation length across the superconducting transition temperature [50], modifications of the dispersion properties of spin waves [49,54], the formation of magnonic band structures [55], as well as metamaterial properties [57].…”

“…Due to the antagonistic spin ordering [56] the interplay of superconductivity and ferromagnetism leads to competing ground states, affecting the spin transport [52] and the dynamics of magnetic moment excitations [48][49][50][51][52][53][54][55]. Exemplary phenomena emerging at microwave frequencies include the generation of superconducting pure spin currents [51], shortening of the quasiparticle charge-imbalance relaxation length across the superconducting transition temperature [50], modifications of the dispersion properties of spin waves [49,54], the formation of magnonic band structures [55], as well as metamaterial properties [57]. In addition, trajectories of moving flux quanta can be imprinted in a soft magnetic layer [58], and guiding and ratchet effects are also being studied for whirl-like spin textures known as skyrmions [59][60][61].…”

Large spin to charge conversion in the topological superconductor β−PdBi2 at room temperature

“…Accordingly, spin injection into superconductors, typically interpreted in terms of quasiparticle or spin-triplet pair mediated transport, is under active investigation [18][19][20][21][22]. The room temperature spin transport parameters of several conventional superconductors (like Nb and NbN) have also been probed by spin pumping measurements [23,24]. As a result, determining the normal-state spin transport properties in β-PdBi2 can also be useful to future spintronics research using TSC.…”