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Review and Analysis of Measurements of the Spin Hall Effect in Platinum

Written By domingo, 17 de abril de 2022 Add Comment Edit

Abstruse

Electric gating can strongly modulate a wide diversity of physical properties in semiconductors and insulators, such as meaning changes of electrical conductivity in silicon, appearance of superconductivity in SrTiO3, the paramagnet–ferromagnet transition in (In,Mn)Equally, and then on. The key to such modulation is charge aggregating in solids. Thus, it has been believed that such modulation is out of reach for conventional metals where the number of carriers is too large. Nonetheless, success in tuning the Curie temperature of ultrathin cobalt gave hope of finally achieving such a degree of control fifty-fifty in metal materials. Here, we show reversible modulation of upwardly to two orders of magnitude of the inverse spin Hall effect—a phenomenon that governs interconversion betwixt spin and charge currents—in ultrathin platinum. Spin-to-charge conversion enables the generation and use of electric and spin currents in the aforementioned device, which is crucial for the futurity of spintronics and electronics.

Introduction

Electrical gating—as an instrument to modulate properties of materials via control of carrier density—became famous in the middle of the 20th century, when research of West. Shockley, Due west.H. Brattain, and J. Bardeen was lauded by the Nobel prize in Physics in 1956. Nowadays, it lies in the technological foundation of our civilization—field upshot transistor, where electric gating controls semiconductor aqueduct and switches device between on- and off-states. Even so, application of electric gating techniques for a long time was restricted to semiconducting materials, where carrier density is depression enough to be tuned by the gate voltage. Nowadays, electric gating is also used to control devices in the emerging field of two-dimensional materials similar graphene and transition element dichalcogenide monolayers. While carrier density for two-dimensional materials can be high, carriers are located at the interface—region where electric gating has the well-nigh influence. In dissimilarity to the cases described to a higher place, metals are bulk materials, and have high carrier density at the same time. Thus, meaning modulation of properties of metals by electric gating was by and large considered out of reach. While electric gating controls carrier density and direct influences conductivity of the cloth, it can be also applied to control any belongings of the fabric that depends on the position of the Fermi level. A few prominent examples include electric gating controlled insulator–superconductor1 and paramagnet–ferromagnet transitionstwo. Lack of such degree of control over physical phenomena in metals, presented a large disadvantage to the functionality of metal devices. Notwithstanding, success in the tuning of the Curie temperature of ultrathin Co gave hope of finally achieving such a degree of command fifty-fifty in metallic materials3.

In 2006, Saitoh et al. converted the pure spin current into the electric charge current using the inverse spin Hall outcome (ISHE) in metal Pt layer4, while Valenzuela et al. detected the same issue in the aluminum channel of lateral spin valve5. The ISHE originates from the spin–orbit interaction within the material. Due to the spin–orbit interaction, the scattering management of the carriers depends on their spin direction. Thus, the ISHE couples spin current with the electric charge current and allows their interconversion: the longitudinal pure spin electric current generates transversal charge current (the ISHE) and vice versa (the spin Hall issue). After the initial prediction6 and experimental detection7 it took almost twenty years until the importance of the effect was recognized by the scientific community. Pt became the dominant material choice to introduce the spin–charge conversion in studied systems due to its big spin Hall angle (which characterizes the efficiency of the conversion between spin and accuse currents) and easy fabrication8,9,ten,11. In contempo years, novel spin–charge conversion effects like spin–charge conversion due to the electric field and spin–orbit coupling at the interface between 2 materials12, or spin–charge conversion via the spin–momentum locking in topological insulatorsthirteen,fourteen,15 challenged the authorization of the ISHE generated by Pt and other heavy metals16. All the same, though some of the aforementioned systems possess higher spin–charge conversion efficiency than ISHE in Pt, at the moment they are very sensitive to interface quality or not robust at room temperature. Through the years, in that location were many attempts to achieve command over the spin–accuse conversion process. Such control was achieved using electrical bias tuning of Schottky bulwark in semiconductors17 and electric gating in the various two-dimensional systemsxviii,19,twenty,21. However, as discussed above, in dissimilarity to semiconductors and two-dimensional systems, electric gating control over spin–accuse conversion via ISHE in metals remained a formidable claiming. Recent studies showed that it is possible to change the ISHE of Pt through composition command of the sample: past either adjusting the number of the scattering centers22,23, or substituting part of Pt atoms with another element24,25. However, tuning of the ISHE in the heavy metals within a single device remained elusive and then far.

In this newspaper, we written report the largest to date modulation of the metal resistivity in ultrathin Pt film through the careful control of Pt thickness and an ionic gate technique. Nosotros show that such command over the carrier density allowed us to tune reversibly and reproducibly the amplitude of the ISHE in Pt over two orders of magnitude—a consequence that tin be used in spin-torque and other spintronics devices that use spin–accuse conversion.

Results

Resistivity and carrier modulation measurements

Figure 1 shows the dependence of the Pt resistivity ρ Pt in logarithmic scale on the changed thickness 1/d Pt and thickness d Pt (a and b, respectively), where each filled circle represents an individual sample. The solid bluish line shows the resistivity calculated using Eq. (23) from the literature26 (which takes into account scattering by both grain boundaries and film surfaces) with values p = 0.viii—fraction of carriers specularly scattered at the surface of Pt layer, bulk resistivity ρ ∞ = twoscore µΩ cm, hateful free path λ mfp = 10 nm and the grain boundary penetration parameter ζ = 0.2526. Experimental data follows the theoretical calculation, which shows that Pt samples were successfully fabricated down to the smallest thickness. The abrupt increase in the Pt resistivity with the decreasing thickness is due to the increased contribution from the surface and grain boundaries handful in the thin layers. The atomic force microscopy measurements (Supplementary Note xi) also confirmed the continuous nature of the Pt films.

Fig. i
figure 1

Thickness dependence of the Pt resistivity. Dependence of the Pt resistivity ρ Pt on a the inverse thickness one/d Pt, b the thickness d Pt. Notation the logarithmic scale of y-axis. Filled circles bear witness the experimental data, line shows the resistivity calculated using Eq. (23) from the literature26 and values ρ ∞ = forty µΩ cm, λ = ten nm, p = 0.eight, ζ = 0.2526. Resistivity of the Pt films increased with the decreasing thickness due to increased contribution from the surface and grain boundaries scattering. See Supplementary Note 3 for farther details

Full size prototype

Effigy 2 shows the schematic prototype of the samples used in the study. Thin Pt films (in the thickness range from 1.5 to 20 nm) were grown on tiptop of the insulating Gadolinium Gallium Garnet (GGG)/Yttrium Iron Garnet (YIG) substrates. We modulated accuse carrier density in our Pt devices with electrical top gate using the ionic liquid technique, which is also commonly referred to as the electrical double-layer transistor method. During the measurement, a sample with the gate was mounted in a vertical position into the crenel of the electron spin resonance system. Figure 3 shows the ratio of the resistivity of the samples measured at gate voltage V Yard = −ii 5 and V G = +2 5: k =R(V Yard = −two V)/R(V K = +2 V). A simple adding using the free electron Drude theory of metals that assumes one gratis electron per atom gives an estimation of the atom and carrier density in Pt n = 6.vi·1022 cm−three. Nonetheless, ring calculations predict smaller number of 0.iv 6s-band electrons per Pt atom27. Experimentally even lower values of 0.24 conduction electrons per Pt atom were measured in thin Pt films, with bulk carrier density calculated to be northward = 1.6·1022 cm−3 28. While Pt is a two-ring conductor with dominating carriers from the closed due south-like Γ-electron and open d-similar X-hole Fermi surfaces27,29,30, the divergence in effective mass and specular reflection of calorie-free electron carriers and heavy pigsty carriers can lead to electron ring dominated conduction in thin films28,31. Using formula \(north = \sqrt {\frac{three}{{8{\mathrm{\pi }}}}} \left( {\frac{{\sigma _\infty }}{{\lambda _{{\mathrm{mfp}}}}}\frac{h}{{{\mathrm{e}}^2}}} \right)^{three/2}\), where e—elementary accuse, h—Planck abiding, and values of σ ∞ and λ mfp obtained from the thickness dependence of resistivity, value of the bulk carrier density in our Pt is estimated to exist north = 6·1021 cm−3, which is the same with result calculated for sparse Pt films from the data reported in the literature26. Carrier density—modulated by the gate voltage in 2 nm-thick sample—is estimated to be n = four.2·x21 cm−3 at 5 Thousand = −2 V, and n = 7.nine·ten21 cm−3 at V G = two V. Thus, induced by the ionic gel carrier density is Δnorthward = ± ii·ten21 cm−three, which gives induced sheet carrier density of Δn sh = Δn·d Pt = 4·x14 cm−two. This value is inside the range of commonly reported carrier density modulation using the ionic liquid: the order of ten14 carriers/cm2 is routinely accomplished, with the highest reported values larger than 1015 carriers/cmtwo 32. Using relation between n and σ from the above, we can theoretically guess \(g = \frac{{R|_{V_{\mathrm{Thou}} = - 2{\mathrm{Five}}}}}{{R|_{V_{\mathrm{G}} = + 2{\mathrm{V}}}}} = \left( {\frac{{d_{{\mathrm{Pt}}} + {\mathrm{\Delta }}n_{{\mathrm{sh}}}/due north}}{{d_{{\mathrm{Pt}}} - {\mathrm{\Delta }}n_{{\mathrm{sh}}}/n}}} \right)^{two/iii}\), where northward = 6·x21 cm−3. Figure iii shows experimentally measured grand for samples with various Pt thickness (royal filled circles), and theoretically estimated 1000 assuming the same induced sheet carrier density in all devices Δn sh = 4.viii·10xiv cm−2 (bluish line). In agreement with theoretical calculation, all devices showed increased resistivity modulation gene k with the decreased thickness (run across Supplementary Notes 4, 5, nine, 14 for farther give-and-take on the resistivity modulation using ionic gel, and Supplementary Annotation 15 for detailed give-and-take on the effect of the accuse screening on gate modulation). Additionally, in thin films resistivity contribution due to the grain hopping can possibly be modulated by the gate voltage application. However, measurements of the temperature dependence of the resistivity indicate that its contribution at 250 K (temperature of the spin pumping and ISHE measurements) is on the order of only a few percent fifty-fifty in 2 nm-thick films (come across Supplementary Notes 16 for detailed give-and-take). We achieved the resistivity modulation k in our samples upwards to 280%: this is more one order of magnitude larger than previously reported in other studies31,33,34,35.

Fig. 2
figure 2

Layout of the experiment. a–c Schematic representation of the carrier density modulation in Pt channel by using tiptop ionic gel gate. a At the negative gate voltage Five G < 0, ions within the ionic gel course negatively charged layer at the interface with Pt, thus decreasing the number of electron carriers available in the channel; b at 5 M = 0, ionic gel is unordered and carrier density in the channel is non modulated; c at Five G > 0, positively charged layer is formed at the interface with Pt leading to increased number of electron carriers in the Pt channel and decreased resistance. d Under the ferromagnetic resonance condition of YIG layer, out-of-aeroplane spin current j s is injected into Pt aqueduct via spin pumping. eastward Changed spin Hall issue, ISHE, inside the Pt channel converts out-of-plane spin current j s into the in-airplane charge current j c. f Schematic top view of the sample. Electromotive forcefulness generated by the ISHE is detected from the Ti/Au electrodes at the ends of the sample. See Supplementary Notes 1, 17 for further details on sample structure and fabrication

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Fig. three
figure 3

Thickness dependence of the Pt resistivity modulation. Dependence of the resistivity modulation cistron grand =R(V G = −ii 5)/R(V G = +two Five) on the thickness of Pt layer d Pt. Blue solid line shows theoretical calculation assuming the aforementioned number of carriers induced in all devices, as described in the main text; purple filled circles are experimental data, each circle corresponds to a divide sample. The blue filled circumvolve is the averaged resistivity modulation k obtained for 2.5 nm sample from 15 gate voltage sweeps (see Supplementary Note 5 for details). In agreement with the theoretical calculation, devices showed increased resistivity modulation factor 1000 with the decreased thickness. Notation the logarithmic scale of x-axis

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Spin–charge conversion measurements

For the ISHE measurements, after setting the gate voltage, we cooled the sample from room temperature to 250 K. Ionic leak current, comparable to the spin–charge conversion current at room temperature in Pt (on the order of nA), is completely suppressed at 250 K, when ion molecules in the ionic gel become immobile. For the details most ionic gel preparation and measurement process, see Methods section. Magnetic field of the microwaves practical to the crenel with sample drives magnetization of the ferrimagnet YIG layer into precession at the sure value of the external magnetic field, known as the ferromagnetic resonance field H FMR 36. Precession of the magnetization induces transfer of the angular momentum from YIG into the adjacent Pt layer without any charge transfer, i.due east., generates pure out-of-plane spin electric current j due south, where spin management is adamant by the direction of the practical static magnetic field. This pure spin current generation method is commonly referred to as the spin pumping37,38. The pure out-of-plane spin current is converted into the in-plane charge current via the ISHE, which is measured at Ti/Au electrodes located at the opposite sides of the samples. Figure 4d shows the electromotive strength generated in the 2 nm-thick Pt sample under the gate voltage of 0 Five during the microwave absorption in YIG layer. The generated pure spin and charge currents are proportional to the captivated microwave power39, thus generated electromotive force follows the Lorentzian shape of the microwave absorption spectrum. Direction of the injected spins σ is reversed together with the direction of the external magnetic field (characterized by angle θ H ), which results in the sign change of the spin–accuse conversion current: j c ∝ j s×σ. In understanding with the ISHE theory, sign of the generated electromotive force was reversed betwixt θ H  = 0° (blue filled circles) and θ H  = 180° (majestic filled circles). Subtracting electromotive force data for the opposite directions of the external magnetic field removes spurious contributions independent of magnetic field (for case, the Seebeck effect). The aamplitude of the ISHE voltage was extracted from the fitting of the magnetic field-averaged electromotive forcefulness \((V_{\theta_{\bf {H}}}=0^{\circ}-V_{\theta_{\bf {H}}}=180^{\circ})/2\) using symmetrical and asymmetrical Lorentzian components (see Supplementary Notes six–8, thirteen for more details, examples of the averaging and fitting process). Figure 4a, b shows a alter in the amplitude of the current and voltage generated by the ISHE in the ii nm-thick Pt sample. In contrast to the microwave absorption spectrum (Fig. 4i–n), electromotive strength generated via the ISHE (Fig. 4c–h) was strongly modulated with the awarding of the gate voltage. The amplitude of the spin–charge conversion current was tuned from the I ISHE =5 ISHE/R = 3.0 nA at V Chiliad = −2 V to I ISHE = 0.ane nA at V G = 2 Five. In our all-time sample, nosotros achieve modulation of the Five ISHE and I ISHE from 100% at V Chiliad = −2 V down to 0.viii% and i.7%, respectively, at V One thousand = 2 V. Figure 5c shows reproducibility of the modulation of the spin–charge conversion current in ii unlike sweeps of the gate voltage for the aforementioned sample and in the different sample with the same Pt thickness d Pt = 2 nm. These results show the successful accomplishment of control over the ISHE in a metallic fabric.

Fig. 4
figure 4

Gate modulation data for the 2 nm-thick Pt sample. a Dependence of the ISHE current amplitude, I ISHE, on the applied gate voltage V G. b Dependence of the ISHE voltage amplitude, V ISHE, on the applied gate voltage V G. c–h Electromotive force measured for the management of the external magnetic field θ H  = 0° (blue filled circles) and θ H  = 180° (purple filled circles), dashed black lines show respective experimental data points in b (V ISHE(V G)); i–due north microwave absorbance spectrum at the ferromagnetic resonance; and o–t drain-source current I DS dependence on the drain-source electric current voltage V DS; at a prepare gate voltage 5 G, where B′ =µ 0(H−H Center). c, i, o 5 Thousand = −2.0 V; d, j, p Five Grand = 0 5; e, thousand, q Five Grand = 1.0 5; f, fifty, r V G = 1.2 5; thousand, 1000, s V G = 1.iv Five; h, n, t V G = 2.0 V. In contrast to the microwave assimilation spectrum (i–n), electromotive force generated via the ISHE (c–h) was strongly modulated with the application of the gate voltage

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Fig. 5
figure 5

Gate command of the spin–charge conversion in thin Pt films. a Resistance modulation under awarding of the gate voltage V Thou for the d Pt = ii nm sample. b Electromotive force detected from d Pt = 2 nm sample for V G = −2.0 V and V G = 2.0 V averaged over contrary directions of the external magnetic field (θ H  = 0° and θ H  = 180°) to remove spurious contributions; |B′| =µ 0(H−H Center). c Comparing of the normalized spin–charge conversion current I ISHE/I ISHE max between different devices, where I ISHE =V ISHE/R—aamplitude of the generated via the ISHE spin–accuse conversion current. Bluish filled circles—Device A with d Pt = 2 nm, majestic filled circles—Device A with d Pt = two nm remeasured, green filled circles—Device B with d Pt = 2 nm (Five ISHE(V K) and R(V 1000) can exist found in Supplementary Note 10), red filled circles—device with d Pt = two.5 nm, gray filled circles—device with d Pt = ten nm. Comparing to the 10 and two.five nm devices, ii.0 nm devices showed larger modulation of the ISHE current, as expected from the carrier density modulation mechanism

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Discussion

In the following paragraph, we show that the ISHE observed in our samples is intrinsic in nature and originates from the inter-d-band excitations. The ISHE spin–charge conversion electric current is given past the equation40, I ISHE =wθ SH λ stanh(d⁄(iiλ s))(2e⁄ℏ)j due south 0, where w—channel width (same for all samples), θ SH—spin Hall angle, λ s—spin diffusion length, d—channel thickness, ℏ—reduced Planck abiding, j due south 0—injected spin current density at the YIG/Pt interface. Also, due to the Elliott–Yafet spin relaxation mechanism41,42 in Pt σ SH =σθ SH ∝ λ south θ SH, where σ SH and σ are spin Hall and electrical conductivities, respectively22,23,43. Disregarding small changes in the factor tanh(d/iiλ s) between different samples (it is close to i for all aqueduct thicknesses because of the scaling of the spin diffusion length with resistivity of Pt samples22,23,43), 1 arrives at: I ISHE≅Aσ SH j s 0, where A =w(λ south/σ)tanh(d⁄(2λ s))(2e⁄ ℏ) can exist considered every bit a constant beyond the samples. Since YIG surface handling and sputtering weather for Pt were identical across all samples, we can assume similar injected spin current density j due south 0 at the Pt/YIG interface. Thus, generated spin–charge conversion current I ISHE from sample to sample was solely controlled by the spin Hall conductivity (SHC) σ SH of the sample: I ISHE≅A′σ SH, where A′ =Aj s 0 is a constant. The ISHE in Pt was theoretically predicted8,44,45 and experimentally confirmedx,xi to be dominated by the intrinsic mechanism, unless the superclean regime is entered (ρ Pt < xv μΩ cm), where extrinsic ISHE cannot be neglected anymore23. Large spin–orbit splitting lifts the double degeneracy of the d-bands most the L and X points at the Fermi level in Pt. Intrinsic ISHE originates from the interband scattering betwixt these orbitals45, and—according to the band calculations—SHC should exhibit a abrupt decrease with increasing resistivity8,44. In dissimilarity, in the previous experimental studies, SHC was measured to exist independent of Pt resistivity22,23,46. While the spin Hall angle of Pt varies greatly among different studies, it was shown to originate from the linear scaling of the spin Hall angle with the resistivity of the sample22,23,43, leaving SHC σ SH =σθ SH unaffected past changes in the resistivity. Thus, to the best of our knowledge, the theoretically predicted dependence of the SHC on the resistivity of textile has never been observed experimentally neither in Pt, nor in other materials. Our loftier-resistivity samples address this discrepancy between the theory and experiment, and access the resistivity-dependent authorities of SHC. All experimental studies and then far were carried out on the low-resistivity Pt samples, where interband excitations that govern SHC are controlled by the ℏ/Δ, where Δ is the spin–orbit-induced splitting of d-bands. In contrast to the low-resistivity regime (ρ Pt < xl μΩ cm), in the loftier-resistivity regime (γ ≫Δ) interband excitations are governed by the quasiparticle lifetime ℏ/γ, which is roughly inversely proportional to resistivity. Figure 6 shows the dependence of the σ SH(ρ)≅I ISHE(ρ)/A′ (calculated using I ISHE measured at V G = 0 V and A′ = 0.05 nA Ω cm) on the resistivity of the samples, which was controlled by the thickness of the Pt layer (see Fig. 1). SHC showed a strong decrease with the resistivity in our samples that followed the ρ −ii dependence (Fig. six dashed blueish line) theoretically predicted for the σ SH 8,44. Our results provide experimental bear witness for the inter-d-band excitations origin of SHC in Pt.

Fig. six
figure 6

Dependence of the spin Hall conductivity on the resistivity of Pt. Purple filled circles show the spin Hall conductivity (SHC) calculated from the experimentally measured spin–charge conversion current I ISHE, bold A′ = 0.05 nA Ω cm; blueish filled circles show SHC σ SH from the ring calculations of Kontani et al.44. The experimentally measured decrease of SHC follows the theoretically predicted ρ −two dependence of the SHC in the high-resistivity regime (dashed blueish line)eight,44. The SHC values are given in ℏ/due east units

Full size prototype

Keeping in heed the inter-d-band transitions nature of the SHC, we discuss a possible machinery of the observed strong suppression of the ISHE at 5 K > 0. As discussed above, in thin films contribution of the s-similar electrons to conduction is dominant, while the contribution from the d-like carriers is small due to the specular reflection and big effective mass. All the same, the main scattering machinery for the s-like conduction electrons is phonon-induced scattering into d-like empty states at the Fermi level, which depends strongly on the density of the d-states. At the same time, the density of states of the d-bands affects the SHC governed by the inter-d-band transitions. Interestingly, band calculations showed that density of the d-states in Pt sharply decreases higher up the Fermi level47. Thus, the upshift of the Fermi level at positive V M should lead to decrease in the resistivity due to the increased number of electrons at Γ bespeak and the decreased scattering charge per unit through the d-states, and subtract in the SHC due to the decreased inter-d-band handful considering of the moving away from the points where the separate d-bands are shut to each other and the decreased number of d-states. This is consistent with our experimentally observed results where the subtract in the sample resistance is followed by the decrease in the spin–accuse conversion electric current generated through the ISHE (Fig. v). Such reduction of the SHC with the tuning of the Fermi level was predicted for the majority Pt, though large suppression of the SHC was estimated to occur on the shift of Fermi level on the order of 1 eV45, which is larger than expected in our example. Nosotros hope that our results will motivate theoretical studies on the Fermi level dependence of the SHC in ultrathin Pt films, where increased scattering and lower carrier density, together with the few-atomic layer thickness of the flick, can pb to a deviation in the SHC in comparison with bulk Pt, which can help to explicate the sharper dependence of the SHC on the position of the Fermi level.

Finally, we note that the anomalous Hall effect (AHE) induced by the proximity to ferrimagnetic insulators48 or gate voltage awarding was reported in sparse Pt films49. Such induced magnetic proximity effect can lead to a reduction of the SHC in Ptl. While the mechanism of the induced magnetic moments that causes the AHE in Pt is still non completely understood, the AHE in Pt was only nowadays at low temperatures below 200 K, and a large part of the gate-induced resistance and the AHE modulation was irreversible48,49. In dissimilarity, we show reversible control over the resistance and the ISHE at T = 250 K (come across Supplementary Note 5 and Fig. 5c). Hence, magnetically induced moments in Pt are expected to emerge at temperature lower than used in our experiments. To confirm this, we carried out Hall measurements in our samples. We observed a clear non-linear component that tin be attributed to the AHE only at 10 K (Supplementary Note 12). Moreover, the negative magnetoresistance in Pt was too attributed to the emergence of the magnetic moments49. We observe switching from the positive to the negative magnetoresistance in d Pt = ii nm sample only at 10 Thou. Thus, magnetic furnishings appear in our organisation at much lower temperature than the 250 Grand, at which spin pumping and spin–accuse conversion experiments were performed. In other study, change in sign of the spin–charge conversion in Pt-based spin-torque structures was reported with the thickness of the Pt layer51,52. However, information technology originated from the spin–accuse conversion at the interface between Pt and oxidized CoFeB layer, which is absent-minded in our case.

Our results provide insight into the fascinating physics of ultrathin Pt films and spin–charge conversion. Through the ionic gel gate, we demonstrated reversible control over the resistivity of Pt film that is i lodge of magnitude larger than was achieved in previous studies. Such control over the carrier density allowed us to tune the ISHE in Pt by two orders of magnitude—a result that tin can exist used in the gate-tunable spin–accuse converters, spin-torque, and other types of spintronics devices. For example, it opens an exciting possibility of the gate-controlled spin–orbit torque magnetoresistive random-access memory (SOT-MRAM), where the spin electric current generated by the spin–charge conversion in the heavy metallic exerts a torque on the free magnetic layer53.

Methods

Sample fabrication procedure

Beneath is the description of the preparation and measurement process for each YIG/Pt sample used in the study. The GGG/YIG (1.iii µm-thick, three mm-long, and 1 mm-wide) (Granopt, Japan) substrate was polished with agglomerate-gratis alumina polishing interruption (fifty nm particle size), and then annealed at 1000 °C in the air temper for ninety min. The Pt layer was sputtered on top of YIG in Ar plasma at a rate 0.6 Å/southward. Afterwards, the Ti(v nm)/Au(100 nm) electrical pads were formed on the sides of the sample by the electron beam evaporation. Ionic gel was prepared using mixture with weight ratio nine.3:0.7:twenty of the PS-PMMA-PS polymer (Polymer Source, Usa), DEME-TFSI ionic liquid (Kanto Chemical, Japan) and Ethyl Propionate (CHiiiCH2COOC2H5, Nacalai Tesque, Nippon). Insulating double-side agglutinative record was placed on the sides of the Pt channel (inside the area covered by Ti/Au electric pads) to provide boosted mechanical support for the gate electrode film, on peak of which it was placed. Gate electrode moving-picture show was mounted after the application of the ionic gel and was located directly higher up the Pt aqueduct. Meet Supplementary Notes ane, 17 for farther details on sample structure and fabrication.

Measurement process

For the measurement, sample was mounted in the TE011 cavity of the electron spin resonance system (JEOL JES-FA200). The applied microwave power was gear up to 1 mW, and the microwave frequency to f = nine.12 GHz. Gate voltage was set up at room temperature; after the evolution of the electric double layer in the ionic gel, sample was cooled to 250 K and I–V characteristics, FMR and ISHE measurements were carried out. Constant nitrogen gas flow was supplied to the cavity with sample, which was just stopped during the refilling of the liquid nitrogen vessel. Schematic layout of the measurement process can be too institute in Supplementary Notation 2.

Data availability

Information measured or analyzed during this study are available from the corresponding authors on reasonable request.

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Acknowledgements

This work was supported in part by MEXT (Innovative Expanse "Nano Spin Conversion Science" KAKENHI No. 26103003), Scientific Research (Southward) "Semiconductor Spincurrentronics" (No. 16H06330), and Grant-in-Help for Young Scientists(A) No. 16H06089. S.D. acknowledges support past JSPS Postdoctoral Fellowship and JSPS KAKENHI Grant No. 16F16064. Authors are grateful to T. Takenobu and J. Pu for the advice on the ionic gel grooming and application.

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Author notes

  1. These authors contributed equally: Sergey Dushenko, Masaya Hokazono.

Affiliations

  1. Department of Electronic Science and Engineering, Kyoto University, Kyoto, 615-8510, Nihon

    Sergey Dushenko, Masaya Hokazono, Yuichiro Ando, Teruya Shinjo & Masashi Shiraishi

  2. Department of Physics Engineering, Mie University, Mie, 514-8507, Japan

    Kohji Nakamura

Contributions

S.D. and Yard.S. designed and supervised the experiment; M.H. prepared the samples and carried out the measurements; S.D. guided the measurements, candy and analyzed the data, and wrote the manuscript; all of the authors contributed to the discussion of the results.

Corresponding authors

Correspondence to Sergey Dushenko or Masashi Shiraishi.

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Dushenko, S., Hokazono, M., Nakamura, K. et al. Tunable inverse spin Hall outcome in nanometer-thick platinum films past ionic gating. Nat Commun 9, 3118 (2018). https://doi.org/10.1038/s41467-018-05611-nine

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