Coherence peak effects in a superconductor induced by a thermal spin current are reported. We measured inverse spin Hall effects induced by spin injection from a ferrimagnetic insulator Y3Fe5O12 into a superconductor NbN using longitudinal spin Seebeck effects. In the vicinity of the superconducting transition temperature of the NbN, a large enhancement of the spin Seebeck voltage is observed, whose sign is opposite to that for the vortex Nernst effect, but is consistent with a calculation for a coherence peak effect in the superconductor NbN.Superconducting spintronics is an emerging research field which explores new spintronic functions by combining superconducting and magnetic orders [1][2][3][4][5]. One of the key ingredients in the superconducting spintronics is generation of spin-polarized carriers in superconductors [6]. In conventional s-wave superconductors, a spinsinglet condensate does not carry spin angular momentum. However, thermally excited quasiparticles (QPs) can carry spin angular momenta even in s-wave superconductors [7]. It was theoretically proposed that spin currents due to the spin-polarized QPs are deflected by spin-orbit scattering to yield a charge imbalance along the Hall direction [8], which can be detected using the technique of the inverse spin Hall effect (ISHE) [9][10][11]. A giant ISHE due to the QP spin current was indeed observed recently by electrical spin injection into an s-wave superconductor NbN in a lateral spin valve structure [12].A spin Seebeck effect (SSE) is one of the useful ways to generate spin current in magnetic heterostructures by applying a temperature gradient [13]. In bilayer systems made up of a ferro-or ferri-magnet (F) and a nonmagnetic metal (N), the SSE enables spin injection from the F layer into the attached N layer through a thermal spin pumping originating in a non-equilibrium spin dynamics [14]. Several theories have been proposed for the mechanism of the SSE [14-17]. Adachi et al. formulated the SSE using the linear-response theory [15,16], where the spin current flowing across the N/F interface reflects spin susceptibilities of both layers and the interface s-d exchange coupling. The injected spin current into the N layer is converted into charge current by ISHE; the ISHE voltage arises in the direction of j s × σ, where j s is the spin current and σ is the spin-polarization vector of electrons in the N layer. Hence ISHE voltage may reflect the spin dynamics of spin-detection layers in SSE measurements according to the theory [15].In this study, we have investigated ISHE induced by SSE in a superconductor/ferrimagnet (S/F) bilayer comprising a superconductor NbN and a ferrimagnetic insulator Y 3 Fe 5 O 12 (YIG). We show that the generated ISHE voltage exhibits an anomalous enhancement just below the superconducting transition. The voltage enhancement can be attributed to a coherence peak effect [18]; according to a theoretical calculation, singularity in the QP density of states at superconducting transition temperature (T c ) leads to an enhance...

Spin current injection from sputtered yttrium iron garnet (YIG) films into an adjacent platinum layer has been investigated by means of the spin pumping and the spin Seebeck effects. Films with a thickness of 83 and 96 nanometers were fabricated by on-axis magnetron rf sputtering at room temperature and subsequent post-annealing. From the frequency dependence of the ferromagnetic resonance linewidth, the damping constant has been estimated to be $(7.0\pm1.0)\times 10^{-4}$. Magnitudes of the spin current generated by the spin pumping and the spin Seebeck effect are of the same order as values for YIG films prepared by liquid phase epitaxy. The efficient spin current injection can be ascribed to a good YIG|Pt interface, which is confirmed by the large spin-mixing conductance $(2.0\pm0.2)\times 10^{18}$ m$^{-2}$.Comment: 6 pages, 4 figure

A rectenna, standing for a rectifying antenna, is an apparatus which generates d.c. electricity from electric fluctuations. It is expected to realize wireless power transmission as well as energy harvesting from environmental radio waves. To realize such rectification, devices that are made up of internal atomic asymmetry such as an asymmetric junction have been necessary so far. Here we report a material that spontaneously generates electricity by rectifying environmental fluctuations without using atomic asymmetry. The sample is a common superconductor without lowered crystalline symmetry, but, just by putting it in an asymmetric magnetic environment, it turns into a rectifier and starts generating electricity. Superconducting vortex strings only annihilate and nucleate at surfaces, and this allows the bulk electrons to feel surface fluctuations in an asymmetric environment: a vortex rectenna. The rectification and generation can be switched on and off with only a slight change in temperature or external magnetic fields.

We propose a method to separate the inverse spin Hall effect (ISHE) from galvanomag- arXiv:1601.03588v1 [cond-mat.mes-hall]

We report on the deformation of microwave absorption spectra and of the inverse spin Hall voltage signals in thin film bilayers of yttrium iron garnet (YIG) and platinum at high microwave power levels in a 9.45-GHz TE 011 cavity. As the microwave power increases from 0.15 to 200 mW, the resonance field shifts to higher values, and the initially Lorentzian spectra of the microwave absorption intensity as well as the inverse spin Hall voltage signals become asymmetric. The contributions from opening of the magnetization precession cone and heating of YIG cannot well reproduce the data. Control measurements of inverse spin Hall voltages on thin-film YIG|Pt systems with a range of line widths underscore the role of spin-wave excitations in spectral deformation.