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We present a theoretical investigation of Majorana zero mode (MZM) assisted spin pumping which consists of a quantum dot (QD) and two normal leads. When the coupling between the MZM and the QD is absent, d.c. pure spin current can be excited by a rotating magnetic field where low energy spin down electrons are flipped to high energy spin up electrons by absorbing photons. However, when the coupling is turned on, the d.c. pure spin current vanishes, and an a.c. charge current emerges with its magnitude independent of the coupling strength. We reveal that this change is due to the formation of a highly localized MZM assisted topological Andreev state at the Fermi level, which allows only the injection of electron pairs with opposite spin into the QD. By absorbing or emitting photons, the electron pairs are separated to opposite spin electrons, and then return back to the lead again, generating an a.c. charge current without spin polarization. We demonstrate the switching from d.c. pure spin current to a.c. charge current based on both Kitaev model and a more realistic topological superconductor nanowire. Although this switching can also be induced by partially separated Andreev bound state (ps-ABS) in the topological trivial phase, it is extremely unstable and highly sensitive to the Zeeman field, which is different from the switching induced by MZM. Our result suggests that quantum spin pumping may be a feasible local transport method for detecting the presence of MZMs at the ends of a superconducting nanowire. [ABSTRACT FROM AUTHOR]

Recently, the altermagnetic materials with spin splitting effect (SSE), have drawn significant attention due to their potential to the flexible control of the spin polarization by the Néel vector. Here, the direct and inverse altermagnetic SSE (ASSE) in the (101)‐oriented RuO2 film with the tilted Néel vector are reported. First, the spin torque along the x‐, y‐, and z‐axis is detected from the spin torque‐induced ferromagnetic resonance (ST‐FMR), and the z‐spin torque emerges when the electric current is along the [010] direction, showing the anisotropic spin splitting of RuO2. Further, the current‐induced modulation of damping is used to quantify the damping‐like torque efficiency (ξDL) in RuO2/Py, and an anisotropic ξDL is obtained and maximized for the current along the [010] direction, which increases with the reduction of the temperature, indicating the present of ASSE. Next, by way of spin pumping measurement, the inverse altermagnetic spin splitting effect (IASSE) is studied, which also shows a crystal direction‐dependent anisotropic behavior and temperature‐dependent behavior. This work gives a comprehensive study of the direct and inverse ASSE effects in the altermagnetic RuO2, inspiring future altermagnetic materials and devices with flexible control of spin polarization. [ABSTRACT FROM AUTHOR]

Recently, the altermagnetic materials with spin splitting effect (SSE), have drawn significant attention due to their potential to the flexible control of the spin polarization by the Néel vector. Here, the direct and inverse altermagnetic SSE (ASSE) in the (101)‐oriented RuO2 film with the tilted Néel vector are reported. First, the spin torque along the x‐, y‐, and z‐axis is detected from the spin torque‐induced ferromagnetic resonance (ST‐FMR), and the z‐spin torque emerges when the electric current is along the [010] direction, showing the anisotropic spin splitting of RuO2. Further, the current‐induced modulation of damping is used to quantify the damping‐like torque efficiency (ξDL) in RuO2/Py, and an anisotropic ξDL is obtained and maximized for the current along the [010] direction, which increases with the reduction of the temperature, indicating the present of ASSE. Next, by way of spin pumping measurement, the inverse altermagnetic spin splitting effect (IASSE) is studied, which also shows a crystal direction‐dependent anisotropic behavior and temperature‐dependent behavior. This work gives a comprehensive study of the direct and inverse ASSE effects in the altermagnetic RuO2, inspiring future altermagnetic materials and devices with flexible control of spin polarization. [ABSTRACT FROM AUTHOR]

Efficient spin sources with large spin Hall angle (θSH) and long spin diffusion length (λSD) are highly desired in the application of spintronic devices. However, due to strong spin‐orbit coupling, the two targets can hardly be achieved simultaneously in conventional relativistic spin sources, like heavy metals. Here, it is proven that collinear antiferromagnetic RuO2 films are able to address this key issue and break the inverse relationship of θSH versus λSD. Based on spin torque‐ferromagnetic resonance and spin pumping measurements, the authors demonstrate that the θSH of RuO2(100) films is 0.183, and the λSD is over 12 nm being an order of magnitude longer than that of Pt, β‐W, and β‐Ta. Meanwhile, sizable λSD is also obtained in spin current with out‐of‐plane spin polarization generated by RuO2(101) films. By conducting a control experiment, the nonrelativistic altermagnetic spin splitting effect (ASSE) is ascertained to be the crucial mechanism accounting for the simultaneous large θSH and long λSD in RuO2. Besides the fundamental significance, these findings will advance the development of spintronics towards higher efficiency and lower power consumption. [ABSTRACT FROM AUTHOR]

Efficient spin sources with large spin Hall angle (θSH) and long spin diffusion length (λSD) are highly desired in the application of spintronic devices. However, due to strong spin‐orbit coupling, the two targets can hardly be achieved simultaneously in conventional relativistic spin sources, like heavy metals. Here, it is proven that collinear antiferromagnetic RuO2 films are able to address this key issue and break the inverse relationship of θSH versus λSD. Based on spin torque‐ferromagnetic resonance and spin pumping measurements, the authors demonstrate that the θSH of RuO2(100) films is 0.183, and the λSD is over 12 nm being an order of magnitude longer than that of Pt, β‐W, and β‐Ta. Meanwhile, sizable λSD is also obtained in spin current with out‐of‐plane spin polarization generated by RuO2(101) films. By conducting a control experiment, the nonrelativistic altermagnetic spin splitting effect (ASSE) is ascertained to be the crucial mechanism accounting for the simultaneous large θSH and long λSD in RuO2. Besides the fundamental significance, these findings will advance the development of spintronics towards higher efficiency and lower power consumption. [ABSTRACT FROM AUTHOR]

The generation of spin current in materials with high spin–orbit coupling is one of the primary topics for future spintronic applications. In this context, the high conversion efficiency of spin current to charge current is desired. Ferromagnetic resonance (FMR)-based inverse spin Hall effect (ISHE) is a quite popular method to study such spin-to-charge conversion. Here microwave frequency plays a crucial role in generating spin current which further gets converted to charge current due to spin–orbit interaction of the given material. In this work, we show the effect of microwave frequency on spin-to-charge current conversion efficiency in La 0. 6 7 Sr 0. 3 3 MnO3/Pt heterostructure prepared by oxygen-assisted molecular beam epitaxy (OMBE). From the ISHE analysis the maximum spin pumping voltage of ∼98 μV has been observed. Further spin Hall angle has been calculated for different frequencies and the maximum calculated value (∼0.06) for this system has been obtained at 14 GHz. [ABSTRACT FROM AUTHOR]

Controlled spin transport in magnetic stacks is required to realize pure spin current-driven logic and memory devices. The control over the generation and detection of the pure spin current is achieved by tuning the spin to charge conversion efficiency of the heavy metal interfacing with ferromagnets. Here, we demonstrate the direct tunability of spin angular momentum transfer and thereby spin pumping, in CoFeB/Pt stack, with interfacial magnetic anisotropy. The ultra-low thickness of the CoFeB thin film by tilting the magnetization from in-plane to out-of plane direction due to interfacial anisotropy from higher thickness of CoFeB thin film. The ferromagnetic resonance measurements are performed to investigate the magnetic anisotropy and spin pumping in CoFeB/Pt stacks. We clearly observe tunable spin pumping effect in the CoFeB/Pt stacks with varying CoFeB thicknesses. The spin current density, with varying ferromagnetic layer thickness, is found to increase from 1.10 MA/m2 to 2.40 MA/m2, with increasing in-plane anisotropy field. Such interfacial anisotropy-controlled generation of pure spin current can potentially lead to next-generation anisotropic spin current-controlled spintronic devices. [ABSTRACT FROM AUTHOR]

Spin pumping and spin-orbit torques play important roles in advancing spintronic device technologies. Our curated special issue focuses on these phenomena in magnetic heterostructures, which are critical for various applications. The high-quality papers1,2,3,4,5,6,7 delve into spin pumping and spin-orbit torques in diverse heterostructures, addressing topics such as insulating/metallic interfaces tailoring spin-to-charge conversion, the influence of HfOx capping layers on perpendicular magnetic anisotropy, anisotropy-controlled spin current generation, sputter pressure-dependent spin Hall angle, the effect of oxygen ion irradiation on spin-orbit torques, and a review paper of emerging two-dimensional/ferromagnetic interfaces. This Editorial discusses the reported articles and the future perspective of these topics. With this special issue, we anticipate significant contributions to both academic research and industrial developments in this direction. [ABSTRACT FROM AUTHOR]

Spin-to-charge conversion and vice versa due to spin-orbit coupling in ferromagnet-heavy metal heterostructure is of paramount interest for developing energy-efficient spintronic devices. Here, we have systematically investigated the effect of Ar deposition pressure ( P Ar ) on the tungsten (W) crystalline phase and extracted spin-dependent transport parameters. X-ray diffraction results show that 10 nm-thick W films exhibit a structural phase transition from a mixed phase of (α + β) -W to a single phase of β -W as a function of P Ar . The observed phase transition is due to a decrease in adatom's energy and surface mobility. Interestingly, only the (α + β) -W phase is found to stabilize when W sputtered on a seed Ni 8 0 Fe 2 0 (Permalloy or Py) film. The growth of (α + β) -W on the seed Py layer could be due to the strain that facilitates the mixed phase. W deposited on the Py layer is shown to be dependent on P Ar , in which the β -W relative phase fraction is relative. A ferromagnetic resonance (FMR)-based spin pumping method was employed for spin current injection. The FMR linewidth (Δ H) is enhanced for Py/W compared to the bare Py layer due to the spin current transport across the interface. The spin-mixing conductance ( g ↑ ↓) is found to be a function of the relative phase fraction of W. The extracted g ↑ ↓ is 4. 9 0 × 1 0 1 8 m − 2 for P Ar = 5 mTorr and 4. 0 5 × 1 0 1 8 m − 2 for P Ar = 1 0 mTorr. From the inverse spin Hall effect (ISHE) measurements, the effective spin Hall angle ((θ SH ) is estimated to be − 0. 1 7 for α -W rich mixed phase of (α + β) -W, whereas it is − 0. 1 0 for β -W rich (α + β) -W. Our systematic study demonstrates the relatively large effective spin Hall angle via low-longitudinal resistivity by controlling the relative phase fraction of W and helps in developing energy-efficient spintronic devices. [ABSTRACT FROM AUTHOR]

Large perpendicular magnetic anisotropy (PMA) and spin-orbit torques are two essential requirements for high-density and energy-efficient spintronic devices. Recent advances in magneto-electric and magneto-ionic control of PMA and spin-orbit torques have opened a pathway to explore different oxide materials with large dielectric constant and high ion mobility. Motivated by interesting memristive properties of HfOx, here, using broadband ferromagnetic resonance measurements, we study the spin pumping in-plane to perpendicularly magnetized W(5 nm)/CoFeB(tCFB) system capped with 4 nm HfOx thin films. We find a large spin pumping and significant PMA strength for HfOx-based thin films. Using ferromagnetic thickness dependence, we also calculate the spin mixing conductance in the trilayer system which is found to be similar to MgO-based thin film stacks. These results will be highly useful for various spintronic applications with electro-static, ionic and memristive gating. [ABSTRACT FROM AUTHOR]

The solid thin films of Py/Pt and Py/W heterostructures have been studied using the ferromagnetic resonance method. The temperature dependences of the Gilbert damping parameter and voltage of the inverse spin Hall effect (ISHE) have been obtained in the 5–290 K temperature range. An abnormal increase in the Gilbert damping parameter in the vicinity of 50 K and a change in the voltage of ISHE has been found. It has been concluded that an increase in the Gilbert damping parameter is of spin-orbital nature. [ABSTRACT FROM AUTHOR]

Magnon, a quanta of spin waves, can transport in magnetically ordered insulators without substantial heat dissipation. The recently demonstrated magnon‐mediated spin torque through antiferromagnetic insulators is regarded as a highly efficient approach for electrical manipulation of magnetization. To control the magnon transport in antiferromagnets, a very large magnetic field is required, since antiferromagnets show immunity to external magnetic disturbance. The antiferromagnetic order can be electrically controlled in multiferroic materials via the magnetoelectric coupling between the antiferromagnetic and ferroelectric orders. Here, we report the experimental observation of magnon spin transport through multiferroic BiFeO3 thin films in SrRuO3/BiFeO3/NiFe tri‐layers at room temperature. We find highly efficient magnon current transmission through BiFeO3 thin film with a thickness exceeding 80 nm by the spin pumping measurement. The magnon spin‐torque efficiency in the tri‐layers measured by the spin‐torque ferromagnetic resonance is comparable with that in the SrRuO3/NiFe bilayer. This results suggest multiferroic BiFeO3 to be an excellent platform for investigating the antiferromagnetic magnon transport and developing magnonic devices. [ABSTRACT FROM AUTHOR]

Abstract Recently, the altermagnetic materials with spin splitting effect (SSE), have drawn significant attention due to their potential to the flexible control of the spin polarization by the Néel vector. Here, the direct and inverse altermagnetic SSE (ASSE) in the (101)‐oriented RuO2 film with the tilted Néel vector are reported. First, the spin torque along the x‐, y‐, and z‐axis is detected from the spin torque‐induced ferromagnetic resonance (ST‐FMR), and the z‐spin torque emerges when the electric current is along the [010] direction, showing the anisotropic spin splitting of RuO2. Further, the current‐induced modulation of damping is used to quantify the damping‐like torque efficiency (ξDL) in RuO2/Py, and an anisotropic ξDL is obtained and maximized for the current along the [010] direction, which increases with the reduction of the temperature, indicating the present of ASSE. Next, by way of spin pumping measurement, the inverse altermagnetic spin splitting effect (IASSE) is studied, which also shows a crystal direction‐dependent anisotropic behavior and temperature‐dependent behavior. This work gives a comprehensive study of the direct and inverse ASSE effects in the altermagnetic RuO2, inspiring future altermagnetic materials and devices with flexible control of spin polarization.

Abstract Magnetic insulators, especially Y3Fe5O12 (YIG), are considered promising candidates for spin‐based device applications due to their ultralow damping, high spin injection efficiency, and long‐distance spin propagation. However, these intriguing features are widely studied based on crystallization YIG films. Pure spin phenomena, like spin transport in YIG films with structural evolution, remain unclear. Herein, pure spin transportation is systematically investigated in the sandwich structure formed by YIG, the inserted layer‐nominal YIG (n‐YIG) with a varied crystalline structure and heavy metal Platinum (Pt). By applying ferromagnetic resonance (FMR)‐driven inverse spin Hall effect (ISHE) measurement, the detected ISHE voltage signal presented a strong correlation with the thickness of n‐YIG and its crystalline phase. A significant increasement in spin transportation is obtained for the crystallized n‐YIG via a high‐temperature annealing. These results demonstrate that pure spin current is transported availably in the structural evolution of YIG films. Furthermore, the element‐specific X‐ray absorption spectroscopy (XAS) and X‐ray magnetic circular dichroism (XMCD) spectra on the n‐YIG films showed a distinction for the crystallized n‐YIG which indicates that the spin propagation is correlated to its magnetic order. These findings are instructive for low‐dissipation spin‐based devices.

Antiferromagnetic (AFM) materials possess a well-recognized potential for ultrafast data processing thanks to their intrinsic ultrafast spin dynamics, absence of stray fields, and large spin transport effects. The very same properties, however, make their manipulation difficult, requiring frequencies in THz range and magnetic fields of tens of Teslas. Switching of AFM order implies going into the nonlinear regime, a largely unexplored territory. Here we use THz light from a free electron laser to drive antiferromagnetic NiO into a highly nonlinear regime and steer it out of nonlinearity with magnetic field from a 33-Tesla Bitter magnet. This demonstration of large-amplitude dynamics represents a crucial step towards ultrafast resonant switching of AFM order.

The injection of pure spin current into the non‐magnetic layer plays a crucial role in transmitting, processing, and storing data information in the realm of spintronics. To understand broadband molecular spintronics, pyrene oligomer film (≈20 nm thickness) was prepared using an electrochemical method forming indium tin oxide (ITO) electrode/pyrene covalent interfaces. Permalloy (Ni80Fe20) films with different nanoscale thicknesses were used as top contact over ITO/pyrene layers to estimate the spin pumping efficiency across the interfaces using broadband ferromagnetic resonance spectra. The spintronic devices are composed of permalloy/pyrene/ITO orthogonal configuration, showing remarkable spin pumping from permalloy to pyrene film. The large spin pumping is evident from the linewidth broadening of 5.4 mT at 9 GHz, which is direct proof of spin angular momentum transfer across the interface. A striking observation is made with the high spin‐mixing conductance of ≈1.02×1018 m−2, a value comparable to the conventional heavy metals. Large spin angular moment transfer was observed at the permalloy‐pyrene interfaces, especially at the lower thickness of permalloy, indicating a strong spinterface effect. Pure spin current injection from ferromagnetic into electrochemically grown pyrene films ensures efficient broadband spin transport, which opens a new area in molecular broadband spintronics. [ABSTRACT FROM AUTHOR]

The topological surface states (TSSs) in topological insulators (TIs) offer exciting prospects for dissipationless spin transport. Common spin-based devices, such as spin valves, rely on trilayer structures in which a non-magnetic layer is sandwiched between two ferromagnetic (FM) layers. The major disadvantage of using high-quality single-crystalline TI films in this context is that a single pair of spin-momentum locked channels spans across the entire film, meaning that only a very small spin current can be pumped from one FM to the other, along the side walls of the film. On the other hand, using nanocrystalline TI films, in which the grains are large enough to avoid hybridization of the TSSs, will effectively increase the number of spin channels available for spin pumping. Here, we used an element-selective, x-ray based ferromagnetic resonance technique to demonstrate spin pumping from a FM layer at resonance through the TI layer and into the FM spin sink. [ABSTRACT FROM AUTHOR]

The purpose of this work is to study the influence of four-magnon (4M) parametric instability on spin pumping by dipole-exchange magnetostatic surface waves (MSSW) with the help of the inverse spin Hall effect (ISHE) in structures based on yttrium-iron garnet (YIG) and platinum (Pt). Methods. The experiments were carried out using the delay line structures based on YIG(900 nm)/Pt(9 nm) where electromotive force (EMF) induced by ISHE demonstrates a growth at the frequencies of the resonant interaction between MSSW and volume exchange modes. The frequency dependencies of the amplitude and phase for the delay line structure and EMF (U(f)) from the platinum layer were studied as a function of the MSSW power. Results. It was shown that the resonant EMF growth at the frequencies of dipole-exchange resonances is caused by the presence of Van Hove singularities in the density of states for spin waves at such frequencies that leads to an increase in the efficiency of electron-magnon scattering at the YIG–Pt interface. A growth in MSSW power beyond the threshold of 4M instability development results in a “smoothing” of resonant particularities in the EMF frequency dependence U(f) that can be explained by decreasing efficiency of spin pumping due to destruction of dipole-exchange resonances and related singularities in the density of states of spin waves. Conclusion. Obtained results may be of interest for the development of highly sensitive spin current detectors, as well as for the implementation of spintronic devices.

In this paper, the dependence of the spin pumping effect on a layer of tungsten disulfide (WS2) by the inverse Hall spin effect (ISHE) is investigated. The precession motion of the magnetization vector creates the effect of spin pumping on a non-conductive ferrimagnetic film. A stream of polarized spin electrons is then injected into the NM layer of a non-magnetic material such as Pt. This spin current is converted to electric current by the ISHE. We investigated the efficiency of spin injection into tungsten disulfide WS and found that as the film thickness increased, the ISHE voltage also increased and compared this relationship with the theory. Next, we obtained the spin diffusion length and conductivity of the spin mixture by varying the damping coefficient of Gilbert with thickness. As far as we know, similar studies have been performed here on materials such as yttrium-iron-garnet or Mo1-xWxS2 alloy, but not on tungsten disulfide. Studies such as the effect of spin-orbit coupling, the study of second-order Riemann scattering, and the like, have been performed on tungsten disulfide and are still ongoing. We hope this will guide for the development of further studies in this field.

Growing concentration on the novel information processing technology and low‐cost, flexible materials make the spintronics and organic materials appealing for the future interdisciplinary investigations. Organic spintronics, in this context, has arisen and witnessed great advances during the past two decades owing to the continuous innovative exploitation of the charge‐contained spin polarized current. Albeit with such inspiring facts, charge‐absent spin angular momentum flow, namely pure spin currents (PSCs) are less probed in organic functional solids. In this review, the past exploring journey of PSC phenomenon in organic materials are retrospected, including non‐magnetic semiconductors and molecular magnets. Starting with the basic concepts and the generation mechanism for PSC, the representative experimental observations of PSC in the organic‐based networks are subsequently demonstrated and summarized, by accompanying explicit discussion over the propagating mechanism of net spin itself in the organic media. Finally, future perspectives on PSC in organic materials are illustrated mainly from the material point of view, including single molecule magnets, complexes for the organic ligands framework as well as the lanthanide metal complexes, organic radicals, and the emerging 2D organic magnets. [ABSTRACT FROM AUTHOR]

We report the impact of the tungsten crystal structure on the spin transport properties of permalloy/tungsten bilayers grown by sputtering on (100) silicon. The microstructure of the tungsten layer was modified using a reactive N 2 /argon mixture during the fabrication process. The analysis combines ferromagnetic resonance and inverse spin Hall effect (ISHE) experiments. A correlation with the electrical and structural characterization indicates that an initial β -W stabilization notably improves the measured ISHE signal. Nevertheless a subsequent increment of the N 2 pressure degrades the signal, probably due to higher interstitial nitrogen and degradation of the interface quality. The interplay between the resistivity and disorder gives an optimal growth condition to enhance the tungsten spin current sensing property. [ABSTRACT FROM AUTHOR]

Abstract Growing concentration on the novel information processing technology and low‐cost, flexible materials make the spintronics and organic materials appealing for the future interdisciplinary investigations. Organic spintronics, in this context, has arisen and witnessed great advances during the past two decades owing to the continuous innovative exploitation of the charge‐contained spin polarized current. Albeit with such inspiring facts, charge‐absent spin angular momentum flow, namely pure spin currents (PSCs) are less probed in organic functional solids. In this review, the past exploring journey of PSC phenomenon in organic materials are retrospected, including non‐magnetic semiconductors and molecular magnets. Starting with the basic concepts and the generation mechanism for PSC, the representative experimental observations of PSC in the organic‐based networks are subsequently demonstrated and summarized, by accompanying explicit discussion over the propagating mechanism of net spin itself in the organic media. Finally, future perspectives on PSC in organic materials are illustrated mainly from the material point of view, including single molecule magnets, complexes for the organic ligands framework as well as the lanthanide metal complexes, organic radicals, and the emerging 2D organic magnets.

In this paper, we report the first theoretical results on the acoustic generation of spin accumulation in ferromagnet-semiconductor-ferromagnet trilayers. As a representative material system, we consider a Ni/GaAs/Ni trilayer coupled to a piezoelectric transducer, which injects a planar acoustic wave into the adjoining Ni film. By combining an analytical solution of the spin diffusion equation in the GaAs spacer with results of numerical simulations of the coupled elastic and magnetic dynamics in the Ni films, we quantify an oscillating inhomogeneous spin accumulation in GaAs. It is found that both dc and ac parts of the mean spin accumulation vary nonmonotonically with the spacer thickness t S , reaching maximal values at t S mostly close to 0.25 or 0.75 of the wavelength of the injected monochromatic acoustic wave. Remarkably, the transverse wave generates the spin accumulation much more efficiently than the longitudinal one. Our theoretical predictions provide guidelines for the development and optimization of energy-efficient acoustic spin injectors into semiconductors, which should have much lower power consumption than injectors driven by the microwave magnetic field. [ABSTRACT FROM AUTHOR]

Spin-pumping-induced damping and interfacial Dzyaloshinskii–Moriya interaction (iDMI) have been studied in Pt/Co2FeAl/MgO systems grown on Si or MgO substrates as a function of Pt and Co2FeAl (CFA) thicknesses. For this, we combined vibrating sample magnetometry (VSM), microstrip ferromagnetic resonance (MS-FMR), and Brillouin light scattering (BLS). VSM measurements of the magnetic moment at saturation per unit area revealed the absence of a magnetic dead layer in both systems, with a higher magnetization at saturation obtained for CFA grown on MgO. The key parameters governing the spin-dependent transport through the Pt/CFA interface, including the spin mixing conductance and the spin diffusion length, have been determined from the CFA and the Pt thickness dependence of the damping. BLS has been used to measure the spin wave non-reciprocity via the frequency mismatch between the Stokes and anti-Stokes lines. iDMI has been separated from the contribution of the interface perpendicular anisotropy difference between Pt/CFA and CFA/MgO. Our investigation revealed that both iDMI strength and spin pumping efficiency are higher for CFA-based systems grown on MgO due to its epitaxial growth confirmed by MS-FMR measurements of the in-plane magnetic anisotropy. This suggests that CFA grown on MgO could be a promising material candidate as a spin injection source via spin pumping and for other spintronic applications. [ABSTRACT FROM AUTHOR]

Improvement of transmission efficiency of spin waves in magnonic devices is crucial for high‐efficiency magnon‐based operations. However, existing techniques for enhancing spin‐wave detection signals, which either improve waveguide material quality or convert other forms of external energy into magnon energy, are still not efficient and convenient enough. Here, it is experimentally demonstrated that low‐k spin waves (where k is the wavenumber) transmission efficiency can be enhanced through yttrium iron garnet (YIG) surface metallization owing to the significantly increased group velocity and low spin‐pumping efficiency at low k. Given that the shielding effect of the conductive metal on YIG increases the spin‐wave group velocity from 55 to 132 km s−1, the weak magnon‐dissipation mechanism of low‐k spin waves provides the foundation for signal enhancement. Through a detailed theoretical analysis on dispersion relations and spin‐wave amplitude, the detected signal strength is increased to 2 times for copper and 2.24 times for gold is verified. In detail the competition between the spin‐pumping effect is discussed and the enhanced group velocity is introduced by the metal decoration. This competition describes the essence of partial signal enhancement in the spin‐wave transmission spectrum. The work provides a practical way to achieve spin‐wave manipulation and low‐loss transmission. [ABSTRACT FROM AUTHOR]

Mn3Sn is a non‐collinear antiferromagnetic quantum material that exhibits a magnetic Weyl semimetallic state and has great potential for efficient memory devices. High‐quality epitaxial c‐plane Mn3Sn thin films have been grown on a sapphire substrate using a Ru seed layer. Using spin pumping induced inverse spin Hall effect measurements on c‐plane epitaxial Mn3Sn/Ni80Fe20, spin‐diffusion length (λMn3Sn$\lambda _{\rm Mn_3Sn}$), and spin Hall conductivity (σSH) of Mn3Sn thin films are measured: λMn3Sn=0.42±0.04$\lambda _{\rm Mn_3Sn}=0.42\pm 0.04$ nm and σSH=−702ℏ/eΩ−1${\sigma}_{\mathrm{SH}}=-702\ \hslash /e\ {\Omega}^{-1}$cm−1. While λMn3Sn$\lambda _{\rm Mn_3Sn}$ is consistent with earlier studies, σSH is an order of magnitude higher and of the opposite sign. The behavior is explained on the basis of excess Mn, which shifts the Fermi level in these films, leading to the observed behavior. These findings demonstrate a technique for engineering σSH of Mn3Sn films by employing Mn composition for functional spintronic devices. [ABSTRACT FROM AUTHOR]

Here, we study the influence of magnetic properties on the spin-pumping effect of the Yttrium Iron Garnet/Platinum (YIG/Pt) bilayer. YIG films were deposited by pulsed laser deposition under variable oxygen pressures. Using broadband ferromagnetic resonance techniques, the magnetic properties of the YIG films were measured. We analyzed the spin-pumping effect in these films by measuring damping changes in samples with and without Pt layers, enabling the calculation of spin-mixing conductance. Experimental results show that films prepared at high oxygen pressure exhibit lower magnetization and reduced spin pumping, α s p , leading to a decreased spin mixing conductance, g ↑ ↓. We report a variation in g ↑ ↓ ranging from 4. 2 × 1 0 18 to 15. 6 × 1 0 18 , m − 2 . These findings underscore the sensitivity of spin transport properties to deposition parameters in YIG-based spintronic devices. • Impact of magnetic properties on the spin-pumping effect in YIG/Pt bilayers. • YIG films prepared at high O 2 pressure exhibit lower α s p , and a decrease in g ↑ ↓. • Sensitivity of spin transport properties to deposition conditions in YIG/Pt bilayers. [ABSTRACT FROM AUTHOR]

• A maximum of 0.25 % MR is observed in Co/PVDF-80 nm/NiFe spin valve devices at 300 K. • Low device resistances are attributed to the mixed PVDF structural phases. • CPW-FMR reveals an efficient spin injection in PVDF/NiFe bilayers. • A 36% enhancement in the Gilbert damping parameter is noted. Room temperature magnetoresistance (MR) across semi-crystalline polyvinylidene fluoride (PVDF) thin films in Ta(2 nm)/Co(15 nm)/PVDF/NiFe(28 nm) pseudo-spin-valve devices (PSVs) are systematically investigated by varying PVDF thicknesses from 80 − 230 nm and applied bias voltages up to 100 mV. NiFe, Ta/Co magnetic bottom and top electrodes, and PVDF thin films are deposited by DC magnetron sputtering and spin-coating methods. The structural, microstructural, and magnetic natures have been evaluated using grazing incidence X-ray diffraction, atomic force microscopy, and magneto optic kerr effect systems. Electrical characteristics reveal a maximum MR of ∼0.25 % at 60 mV bias voltage across PVDF-80 nm and ∼0.08 % across PVDF-230 nm & PVDF- 120 nm devices. A constant MR is found across all the devices up to 100 mV applied bias voltages. In addition to the electrical spin injection evaluation, coplanar waveguide ferromagnetic resonance measurements are utilized to validate the spin injection into PVDF layers by estimating the Gilbert damping parameters of NiFe and PVDF/NiFe bilayers. Furthermore, low MR in PSVs is discussed with the parallel spin-dependent conducting channels corresponding to PVDF's amorphous, alpha, and beta crystalline phases. [ABSTRACT FROM AUTHOR]

Abstract Improvement of transmission efficiency of spin waves in magnonic devices is crucial for high‐efficiency magnon‐based operations. However, existing techniques for enhancing spin‐wave detection signals, which either improve waveguide material quality or convert other forms of external energy into magnon energy, are still not efficient and convenient enough. Here, it is experimentally demonstrated that low‐k spin waves (where k is the wavenumber) transmission efficiency can be enhanced through yttrium iron garnet (YIG) surface metallization owing to the significantly increased group velocity and low spin‐pumping efficiency at low k. Given that the shielding effect of the conductive metal on YIG increases the spin‐wave group velocity from 55 to 132 km s−1, the weak magnon‐dissipation mechanism of low‐k spin waves provides the foundation for signal enhancement. Through a detailed theoretical analysis on dispersion relations and spin‐wave amplitude, the detected signal strength is increased to 2 times for copper and 2.24 times for gold is verified. In detail the competition between the spin‐pumping effect is discussed and the enhanced group velocity is introduced by the metal decoration. This competition describes the essence of partial signal enhancement in the spin‐wave transmission spectrum. The work provides a practical way to achieve spin‐wave manipulation and low‐loss transmission.

In this paper, spin-to-charge current conversion properties in the Weyl semimetal TaP by means of the inverse Rashba-Edelstein effect (IREE) with the interfacial integration of this quantum material with the ferromagnetic metal Permalloy (Py = Ni81Fe19) are presented. The spin currents are generated in the Py layer by the spin pumping effect (SPE) from microwave-driven ferromagnetic resonance and are detected by a dc voltage along the TaP crystal, at room temperature. A field-symmetric voltage signal is observed without the contamination of asymmetrical lines due to spin rectification effects observed in studies using metallic ferromagnets. The observed voltage is attributed to spin-to-charge current conversion based on the IREE, made possible by the spin-orbit coupling induced intrinsically by the bulk band structure of Weyl semimetals. The measured IREE coefficient λIREE = (0.30 ± 0.01) nm is two orders of magnitude larger than in graphene and is comparable to or larger than the values reported for some metallic interfaces and for several topological insulators. [ABSTRACT FROM AUTHOR]

Topological electronic materials hold great promise for revolutionizing spintronics, owing to their topological protected, spin-polarized conduction edge or surface state. One of the key bottlenecks for the practical use of common binary and ternary topological insulator materials is the large defect concentration that leads to a high background carrier concentration. Elemental tin in its α-phase is a room temperature topological semimetal, which is intrinsically less prone to defect-related shortcomings. Recently, the growth of ultrathin α-Sn films on ferromagnetic Co surfaces has been achieved; however, thicker films are needed to reach the 3D topological Dirac semimetallic state. Here, the growth of α-Sn films on Co at cryogenic temperatures was explored. Very low-temperature growth holds the promise of suppressing undesired phases, alloying across the interfaces, as well as the formation of Sn pillars or hillocks. Nevertheless, the critical Sn layer thickness of ≈3 atomic layers, above which the film partially transforms into the undesired b-phase, remains the same as for room-temperature growth. From ferromagnetic resonance studies, and supported by electron microscopy, it can be concluded that for cryogenic Sn layer growth, the interface between Sn and Co remains sharp and the magnetic properties of the Co layer stay intact. [ABSTRACT FROM AUTHOR]

The spin-to-charge conversion in Permalloy (Py)/Cu/Bi2Se3 is tunable by changing the Cu layer thickness. The conversion rate was studied using the spin pumping technique. The inverse Edelstein effect (IEE) length λIEE is found to increase up to ~2.7 nm when a 7 nm Cu layer is introduced. Interestingly, the maximized λIEE is obtained when the effective spin-mixing conductance (and thus Js) is decreased due to Cu insertion. The monotonic increase in λIEE with decreasing Js suggests that the IEE relaxation time (τ) is enhanced due to the additional tunnelling barrier (Cu layer) that limits the interfacial transmission rate. The results demonstrate the importance of interface engineering in the magnetic heterostructure of Py/topological insulators (TIs), the key factor in optimizing spin-to-charge conversion efficiency. [ABSTRACT FROM AUTHOR]

Abstract Topological electronic materials hold great promise for revolutionizing spintronics, owing to their topological protected, spin‐polarized conduction edge or surface state. One of the key bottlenecks for the practical use of common binary and ternary topological insulator materials is the large defect concentration that leads to a high background carrier concentration. Elemental tin in its α‐phase is a room temperature topological semimetal, which is intrinsically less prone to defect‐related shortcomings. Recently, the growth of ultrathin α‐Sn films on ferromagnetic Co surfaces has been achieved; however, thicker films are needed to reach the 3D topological Dirac semimetallic state. Here, the growth of α‐Sn films on Co at cryogenic temperatures was explored. Very low‐temperature growth holds the promise of suppressing undesired phases, alloying across the interfaces, as well as the formation of Sn pillars or hillocks. Nevertheless, the critical Sn layer thickness of ≈3 atomic layers, above which the film partially transforms into the undesired b‐phase, remains the same as for room‐temperature growth. From ferromagnetic resonance studies, and supported by electron microscopy, it can be concluded that for cryogenic Sn layer growth, the interface between Sn and Co remains sharp and the magnetic properties of the Co layer stay intact.

Abstract In this paper, spin‐to‐charge current conversion properties in the Weyl semimetal TaP by means of the inverse Rashba–Edelstein effect (IREE) with the interfacial integration of this quantum material with the ferromagnetic metal Permalloy (Py = Ni81Fe19) are presented. The spin currents are generated in the Py layer by the spin pumping effect (SPE) from microwave‐driven ferromagnetic resonance and are detected by a dc voltage along the TaP crystal, at room temperature. A field‐symmetric voltage signal is observed without the contamination of asymmetrical lines due to spin rectification effects observed in studies using metallic ferromagnets. The observed voltage is attributed to spin‐to‐charge current conversion based on the IREE, made possible by the spin–orbit coupling induced intrinsically by the bulk band structure of Weyl semimetals. The measured IREE coefficient λIREE = (0.30 ± 0.01) nm is two orders of magnitude larger than in graphene and is comparable to or larger than the values reported for some metallic interfaces and for several topological insulators.

Although the spin Hall effect provides a pathway for efficient and fast current‐induced manipulation of magnetization, application of spin–orbit torque magnetic random access memory with low power dissipation is still limited to spin Hall materials with low spin Hall angles or very high resistivities. This work reports a group of spin Hall materials, Pt1−x(TiO2)x nanocomposites, that combines a giant spin Hall effect with a low resistivity. The spin Hall angle of Pt1−x(TiO2)x in an yttrium iron garnet/Pt1−x(TiO2)x double‐layer heterostructure is estimated from a combination of ferromagnetic resonance, spin pumping, and inverse spin Hall experiments. A giant spin Hall angle 1.607 ± 0.04 is obtained in a Pt0.94(TiO2)0.06 nanocomposite film, which is an increase by an order of magnitude compared with 0.051 ± 0.002 in pure Pt thin film under the same conditions. The great enhancement of spin Hall angle is attributed to strong side‐jump induced by TiO2 impurities. These findings provide a new nanocomposite spin Hall material combining a giant spin Hall angle, low resistivity and excellent process compatibility with semiconductors for developing highly efficiency current‐induced magnetization switching memory devices and logic devices. [ABSTRACT FROM AUTHOR]

Spin mixing conductance at the ferromagnet (FM)/heavy metal (HM) interface is a key parameter to estimate the spin current injection into heavy metal. The electrical detection of such injected spin current in heavy metal is possible via inverse spin Hall effect (ISHE). Herein, a large spin mixing conductance in the range of (4.95−6.52) × 1018 m−2 in Ta/permalloy(Py) bilayer structures is reported. In‐plane angular‐dependent ISHE voltage measurements in Ta/Py samples reveal the dominance of spin pumping voltage component over the other spin rectification contributions. Voltage contribution due to spin pumping and anisotropic magnetoresistance (AMR) increases with the Py thickness due to the enhancement in spin pumping and increase in spin‐dependent scattering, respectively. Anomalous Hall effect (AHE) contribution in Py is found to be relatively small. [ABSTRACT FROM AUTHOR]

The quest for quantum phenomena in unconventional materials has led to the development of myriad unique systems. Because of their unusual atomic-scale interface properties and their controllability, graphene/ferromagnet heterostructures have emerged as a strong contender for next-generation spintronics. Further development demands superior properties and correlation between the different microscopic mechanisms involved. Herein, we demonstrate a superior interfacial Dzyaloshinskii–Moriya interaction (iDMI) in single-layer graphene/CoFeB/SiO2 heterostructures from asymmetric spin-wave dispersion measurement using a Brillouin light-scattering technique. The spin-wave frequencies and line widths have been correlated with structural and nanoscale morphological properties to evaluate the roles of Rashba shift and defect density for the emergence of iDMI and spin pumping for a range of thicknesses of the CoFeB layer, where the defects have been found to play a dominant role for the extrinsic spin–orbit coupling over the Rashba shift. A significantly large iDMI and spin-mixing conductance have been observed even at moderately low Ar pressure during sputter deposition of the ferromagnetic layer, which asserts further optimization of the said properties with external deposition parameters for application in next-generation energy-efficient and miniaturized spintronic and spin–orbitronic devices. [ABSTRACT FROM AUTHOR]

Abstract Although the spin Hall effect provides a pathway for efficient and fast current‐induced manipulation of magnetization, application of spin–orbit torque magnetic random access memory with low power dissipation is still limited to spin Hall materials with low spin Hall angles or very high resistivities. This work reports a group of spin Hall materials, Pt1−x(TiO2)x nanocomposites, that combines a giant spin Hall effect with a low resistivity. The spin Hall angle of Pt1−x(TiO2)x in an yttrium iron garnet/Pt1−x(TiO2)x double‐layer heterostructure is estimated from a combination of ferromagnetic resonance, spin pumping, and inverse spin Hall experiments. A giant spin Hall angle 1.607 ± 0.04 is obtained in a Pt0.94(TiO2)0.06 nanocomposite film, which is an increase by an order of magnitude compared with 0.051 ± 0.002 in pure Pt thin film under the same conditions. The great enhancement of spin Hall angle is attributed to strong side‐jump induced by TiO2 impurities. These findings provide a new nanocomposite spin Hall material combining a giant spin Hall angle, low resistivity and excellent process compatibility with semiconductors for developing highly efficiency current‐induced magnetization switching memory devices and logic devices.

Effective spin mixing conductance (ESMC) across the nonmagnetic metal (NM)/ferromagnet interface, spin Hall conductivity (SHC), and spin diffusion length (SDL) in the NM layer govern the functionality and performance of pure spin current devices. It is shown that all three parameters can be tuned significantly via the spin orbit coupling (SOC) strength of the NM layer by virtue of the unique Pd1-xPtx/Y3Fe5O12 system. Surprisingly, the ESMC is observed to increase significantly with x changing from 0 to 1.0, due to the enhanced local density of states for Pt-rich alloys. The SHC in PdPt alloys turns out to be dominated by the skew scattering term. In particular, the skew scattering parameter has for the first time been rigorously demonstrated to increase with increasing SOC strength. Meanwhile, the SDL is found to decrease when Pd atoms are replaced by heavier Pt atoms, validating the SOC induced spin flip scattering model in polyvalent PdPt alloys. A thorough grasp of the dependence of these parameters on the SOC strength in the present work can help to develop a better theoretical graph on the physics of SOC and spin orbit torque switching, relevant to next generation spintronic devices.

Spin‐orbit torques generated by exfoliated layers of the low‐symmetry semi‐metal ZrTe3 are measured using the spin‐torque ferromagnetic resonance (ST‐FMR) technique. When the ZrTe3 has a thickness greater than about 10 nm, artifacts due to spin pumping and/or resonant heating can cause the standard ST‐FMR analysis to overestimate the true magnitude of the torque efficiency by as much as a factor of 30, and to indicate incorrectly that the spin‐orbit torque depends strongly on the ZrTe3 layer thickness. Artifact‐free measurements can still be achieved over a substantial thickness range by the method developed recently to detect ST‐FMR signals in the Hall geometry as well as the longitudinal geometry. ZrTe3/Permalloy samples generate a conventional in‐plane anti‐damping spin torque efficiency ξ||DL$\xi _{||}^{\text{DL}}$ = 0.014 ± 0.004, and an unconventional in‐plane field‐like torque efficiency |ξ||FL|$|\xi _{||}^{\text{FL}}|$ = 0.003 ± 0.001. The out‐of‐plane anti‐damping torque is negligible. It is suggested that artifacts similarly interfere with the standard ST‐FMR analysis for other van der Waals samples thicker than about 10 nm. [ABSTRACT FROM AUTHOR]

Spin‐charge interconversion phenomena at the interface between magnetic materials and topological insulators (TIs) are attracting enormous interest in the research effort toward the development of fast and ultra‐low power devices for future information and communication technology. A large spin‐to‐charge (S2C) conversion efficiency in Au/Co/Au/Sb2Te3/Si(111) heterostructures based on Sb2Te3 TIs grown by metal–organic chemical vapor deposition on 4″ Si(111) substrates is reported. By conducting room temperature spin pumping ferromagnetic resonance, a 250% enhanced charge current due to spin pumping in the Sb2Te3‐containing system is measured when compared to the reference Au/Co/Au/Si(111). The corresponding inverse Edelstein effect length λIEE ranges from 0.28 to 0.61 nm, depending on the adopted methodological analysis, with the upper value being so far the largest observed for the second generation of 3D chalcogenide‐based TIs. These results open the path toward the use of chemical methods to produce TIs on large area Si substrates and characterized by highly performing S2C conversion, thus marking a milestone toward future technology‐transfer. [ABSTRACT FROM AUTHOR]

One of the cornerstone effects in spintronics is spin pumping by dynamical magnetization that is steadily precessing (around, for example, the z -axis) with frequency ω _0 due to absorption of low-power microwaves of frequency ω _0 under the resonance conditions and in the absence of any applied bias voltage. The two-decades-old ‘standard model’ of this effect, based on the scattering theory of adiabatic quantum pumping, predicts that component $I^{S_z}$ of spin current vector $\big( I^{S_x}(t),I^{S_y}(t),I^{S_z} \big) \propto \omega_0$ is time-independent while $I^{S_x}(t)$ and $I^{S_y}(t)$ oscillate harmonically in time with a single frequency ω _0 whereas pumped charge current is zero $I \equiv 0$ in the same adiabatic $\propto \omega_0$ limit. Here we employ more general approaches than the ‘standard model’, namely the time-dependent nonequilibrium Green’s function (NEGF) and the Floquet NEGF, to predict unforeseen features of spin pumping: namely precessing localized magnetic moments within a ferromagnetic metal (FM) or antiferromagnetic metal (AFM), whose conduction electrons are exposed to spin–orbit coupling (SOC) of either intrinsic or proximity origin, will pump both spin $I^{S_\alpha}(t)$ and charge I ( t ) currents. All four of these functions harmonically oscillate in time at both even and odd integer multiples $N\omega_0$ of the driving frequency ω _0 . The cutoff order of such high harmonics increases with SOC strength, reaching $N_\mathrm{max} \simeq 11$ in the one-dimensional FM or AFM models chosen for demonstration. A higher cutoff $N_\mathrm{max} \simeq 25$ can be achieved in realistic two-dimensional (2D) FM models defined on a honeycomb lattice, and we provide a prescription of how to realize them using 2D magnets and their heterostructures.

Spin pumping from a metallic ferromagnet (FM) into an insulating antiferromagnet has been studied across the magnetic phase transition by means of temperature-dependent, broad-band ferromagnetic resonance (FMR) experiments. A set of spin pumping heterostructures consisting of Permalloy (Ni _80 Fe _20 ) as FM and Zn $_{1-x}$ Co _x O with $x = 0.3, 0.5$ and 0.6 (Co:ZnO) as partially compensated antiferromagnetic insulator has been used for which previous experiments have already pointed out the possibility of the existence of spin-pumping. The present experiments allow to reliably separate the various contributions of the temperature-dependent Gilbert damping parameter to the FMR line-width. A careful analysis of the obtained data demonstrates a significant increase of the temperature-dependence of the Gilbert damping parameter $\alpha(T)$ around the magnetic phase transition of Co:ZnO which extends up to room temperature, confirming spin pumping into the fluctuating spin sink of an antiferromagnetic/paramagnetic insulator.

In this study, we investigate the spin-momentum locking phenomenon on Rashba states of antimony (Sb) films. Utilizing spin pumping in conjunction with an external charge current, we uncover the topological properties of Sb surface states. Our key finding is the precise manipulation of the direction and magnitude of the charge current generated by the inverse Rashba-Edelstein effect. This control is achieved through the dynamic interaction between out-of-equilibrium pumped spins and spin-momentum-locked flowing spins, which are perpendicular to the charge current. Our results highlight Sb as a promising material for both fundamental and applied spintronics research. The studied Sb nanostructures demonstrate potential for the development of low-power logic gates operating with currents in the microampere range, paving the way for advanced spintronic applications.

Recently, the altermagnetic materials with spin splitting effect (SSE), have drawn significant attention due to their potential to the flexible control of the spin polarization by the Néel vector. Here, the direct and inverse altermagnetic SSE (ASSE) in the (101)-oriented RuO 2 film with the tilted Néel vector are reported. First, the spin torque along the x-, y-, and z-axis is detected from the spin torque-induced ferromagnetic resonance (ST-FMR), and the z-spin torque emerges when the electric current is along the [010] direction, showing the anisotropic spin splitting of RuO 2 . Further, the current-induced modulation of damping is used to quantify the damping-like torque efficiency (ξ DL ) in RuO 2 /Py, and an anisotropic ξ DL is obtained and maximized for the current along the [010] direction, which increases with the reduction of the temperature, indicating the present of ASSE. Next, by way of spin pumping measurement, the inverse altermagnetic spin splitting effect (IASSE) is studied, which also shows a crystal direction-dependent anisotropic behavior and temperature-dependent behavior. This work gives a comprehensive study of the direct and inverse ASSE effects in the altermagnetic RuO 2 , inspiring future altermagnetic materials and devices with flexible control of spin polarization., (© 2024 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

Large‐area antimony telluride (Sb2Te3) thin films are grown by a metal organic chemical vapor deposition technique on 4" Si(111) substrates, and their topological character probed by magnetoconductance measurements. When interfaced with Fe thin films, broadband ferromagnetic resonance spectroscopy (BFMR) shows a clear increase of the damping parameter in Fe/Sb2Te3 when compared to a reference Fe layer, which may suggest the occurrence of spin pumping (SP) into Sb2Te3. Simultaneously, X‐ray reflectivity and conversion electron Mossbauer spectroscopy evidence the development of a chemically and magnetically pure Fe/Sb2Te3 interface. However, by conducting SP‐FMR, it is shown that no spin‐to‐charge conversion (S2C) occurs in Fe/Sb2Te3, while a clear SP signal develops by introducing a 5 nm Au interlayer between Fe and Sb2Te3, with a measured inverse Edelstein effect conversion efficiency of λIEE = 0.27 nm. The results shed some light on the correlation among the chemical‐structural‐magnetic properties of the Fe/Sb2Te3 interface, the broadening of the magnetic damping parameter as detected by BFMR, and the occurrence of S2C, as probed by SP‐FMR. [ABSTRACT FROM AUTHOR]

Spin pumping is an interfacial spin current generation from the ferromagnetic layer to the non-magnetic metal at its interface. The polarization of the pumped spin current J s ∝ m × m ˙ depends on the dynamics of the magnetic moment m . When the materials are based on light transition metals, mechanism behind the spin current transfer is dominated by the exchange interaction between spin of localized d-electrons and itinerant conduction electrons. In heavier transition metals, however, the interaction is not limited to the exchange interaction. The spin of the conduction electron can interact to its nuclear spin by means of hyperfine interaction, as observed in the shift of NMR frequency. By studying the spin polarization of conduction electron of the non-magnetic metallic layer due to a nuclear magnetic moment I of the ferromagnetic layer, we show that the hyperfine interaction can mediate the spin pumping. The polarization of the spin current generation is shown to have a similar form J s ∝ I × I ˙ . [ABSTRACT FROM AUTHOR]