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We show that the temperature measurement sensitivity in the lock-in thermoreflectance (LITR) can be improved by incorporating a thermochromic liquid crystal (TLC) into a transducer. The quantitatively estimated thermoreflectance coefficient of a TLC/Pt hybrid film depends on the excitation frequency and reaches >2 × 10−2 K−1 at low excitation frequencies, which is two orders of magnitude greater than typical values of 10−4 for metallic films. Using the TLC/Pt film, we detected the temperature changes due to Joule heating and the spin Peltier effect with the temperature resolution of ∼10 μK by the LITR method. We also performed the same measurements for an Au film and found that the temperature resolution for the TLC/Pt film is increased by a factor of >10 compared with that for the Au film despite the low reflected light intensity of the TLC/Pt film.

This article shows experimentally that an external electric field affects the velocity of the longitudinal acoustic phonons ( v LA ), thermal conductivity (κ), and diffusivity ( D ) in a bulk lead zirconium titanate–based ferroelectric. Phonon conduction dominates κ, and the observations are due to changes in the phonon dispersion, not in the phonon scattering. This gives insight into the nature of the thermal fluctuations in ferroelectrics, namely, phonons labeled ferrons that carry heat and polarization. It also opens the way for phonon-based electrically driven all-solid-state heat switches, an enabling technology for solid-state heat engines. A quantitative theoretical model combining piezoelectric strain and phonon anharmonicity explains the field dependence of v LA , κ, and D without any adjustable parameters, thus connecting thermodynamic equilibrium properties with transport properties. The effect is four times larger than previously reported effects, which were ascribed to field-dependent scattering of phonons.

A 47-year-old Japanese man was referred to our hospital because of a sustained high fever with diarrhea 12 days after a flight from India. Liver enzymes were elevated with rose spots, hepatosplenomegaly, relative bradycardia, and acute cholecystitis. A liver biopsy depicted the dense infiltration of lymphocytes and Kupffer cells in sinusoids and the granulomatous formation in the parenchyma. The liver damage was initially resolved with the administration of ceftriaxone for 16 days but flared up 1 week later. Laboratory tests yielded positive reactions for Salmonella typhi and hepatitis E virus RNA. The pathophysiological presentations of concurrent typhoid and type E hepatitis are discussed.

We identify the bosonic excitations in ferroelectrics that carry electric dipoles from the phenomenological Landau-Ginzburg-Devonshire theory. The "ferron"quasiparticles emerge from the concerted action of anharmonicity and broken inversion symmetry. In contrast to magnons, the transverse excitations of the magnetic order, the ferrons in displacive ferroelectrics are longitudinal with respect to the ferroelectric order. Based on the ferron spectrum, we predict temperature-dependent pyroelectric and electrocaloric properties, electric-field-tunable heat and polarization transport, and ferron-photon hybridization.

The Thomson effect induces heat release or absorption under the simultaneous application of a charge current and a temperature gradient to conductors. Here, we theoretically investigate the temperature profile due to the Thomson-effect-induced heat release/absorption in junctionless single conductors which can be a simple temperature modulator. We also perform analysis of the temperature profile for realistic conductors. As a result, we find that, for a conductor with a large Thomson coefficient, the temperature derivative of the Seebeck coefficient, the Thomson-effect-induced heat absorption overcomes the Joule heating, resulting in current-induced cooling in the bulk region. We also elucidate that a feedback effect of the Thomson effect stabilizes the system temperature to one-side of the heat bath, which reflects the fact that the Thomson effect is dependent on the position and proportional to the local temperature gradient. This work will be the basis for thermal management utilizing the Thomson effect., Comment: 15 pages, 7 figures, 2 tables

When a temperature gradient is applied to a closed circuit comprising two different conductors, a charge current is generated via the Seebeck effect1. Here, we utilize the Seebeck-effect-induced charge current to drive 'transverse' thermoelectric generation, which has great potential for energy harvesting and heat sensing applications owing to the orthogonal geometry of the heat-to-charge-current conversion2-9. We found that, in a closed circuit comprising thermoelectric and magnetic materials, artificial hybridization of the Seebeck effect into the anomalous Hall effect10 enables transverse thermoelectric generation with a similar symmetry to the anomalous Nernst effect11-27. Surprisingly, the Seebeck-effect-driven transverse thermopower can be several orders of magnitude larger than the anomalous-Nernst-effect-driven thermopower, which is clearly demonstrated by our experiments using Co2MnGa/Si hybrid materials. The unconventional approach could be a breakthrough in developing applications of transverse thermoelectric generation.

The temperature and yttrium-iron-garnet (YIG) thickness dependences of the spin Peltier effect (SPE) have been investigated using a Pt/YIG junction system at temperatures ranging from room temperature to the Curie temperature of YIG by the lock-in thermography method. By analyzing the YIG thickness dependence using an exponential decay model, the characteristic length of SPE in YIG is estimated to be 0.9 $\mu$m near room temperature and almost constant even near the Curie temperature. The high-temperature behavior of SPE is clearly different from that of the spin Seebeck effect, providing a clue for microscopically understanding the reciprocal relation between them., Comment: 11 pages, 4 figures

Testicular epidermoid cysts are relatively rare, accounting for about 1% of all testicular tumors, and are often treated by high orchiectomy. We describe here the case of a testicular epidermoid cyst treated by testicle-sparing surgery due to a preoperative diagnosis. A 23-year-old man complained of a painless mass in the right scrotum. Physical examination revealed a firm little fingertip-sized smooth-surfaced mass in the right testis. Ultrasonography showed a hypoechoic lesion with an echogenic rim in the right testis. A T2-weighted magnetic resonance image showed a well-demarcated mass with a low signal outline. On the basis of a preoperative diagnosis of epidermoid cyst, intraoperative testicular frozen section was performed, and the mass was resected surgically while preserving the testis.

Magnons are the elementary excitations of the magnetic order that carry spin, momentum, and energy. Here we compare the magnon with the ferron, i.e. the elementary excitation of the electric dipolar order that transports polarization and heat in ferroelectrics., Comment: Submitted for publication in the Virtual Special Issue (VSI) on Magnonics of the Journal of Magnetism and Magnetic Materials, in honor of Prof. Servio Rezende's 80th birthday

We report on a direct measurement method for electrocaloric effects, the heating/cooling upon application/removal of an electric field in dielectric materials, based on a lock-in thermography technique. By use of sinusoidal excitation and multi-harmonic detection, the actual temperature change can be measured by a single measurement in the frequency domain even when the electrocaloric effect shows a nonlinear response to the excitation field. We demonstrated the method by measuring the temperature dependence of the electric-field-induced temperature change in two Sr-doped BaTiO3 systems with different ferroelectric-paraelectric phase transition temperatures, where we introduce the procedure for extracting the pure electrocaloric contribution free from heat losses and Joule heating due to leakage currents. This method can be used irrespective of the type of dielectric material and enables simultaneous estimation of the polarization change and power dissipation during the application of an electric field, making it a convenient imaging measurement method for the electrocaloric effect.

We have investigated the spin-wave dynamics in a one-dimensional magnonic crystal (MC) with respect to the heat radiation due to the damping of the spin waves. The spin waves were excited by applying microwaves via a wire antenna. The heat induced by the excitation and propagation of spin waves was measured using the lock-in thermography (LIT) technique by periodically modulating the microwave power. The LIT measurements resolved the heat source distributions inside the MC, which is made of an yttrium iron garnet film and periodic grooves with a sub-mm interval, in the backward volume wave geometry. The temperature distribution induced by the spin-wave excitation notably depends on the frequency or wave number of the spin waves, as a result of the formation of rejection bands in the MC. The observed temperature modulation profiles are complicated, but their behavior is consistent with a calculation based on the microwave transmission line approximation of the MCs, demonstrating the applicability of the LIT measurements to the investigation of the spin-wave dynamics in sub-mm scale MCs.

We formulate a scattering theory of polarization and heat transport through a ballistic ferroelectric point contact. We predict a polarization current under either an electric field or a temperature difference that depends strongly on the direction of the ferroelectric order and can be detected by its magnetic stray field and associated thermovoltage and Peltier effect.

We demonstrate a method for the simultaneous determination of the thermoelectric figure of merit of multiple martials by means of the lock-in thermography (LIT) technique. This method is based on the thermal analyses of the transient temperature distribution induced by the Peltier effect and Joule heating, which enables high-throughput estimation of the thermal diffusivity, thermal conductivity, volumetric heat capacity, Seebeck or Peltier coefficient of the materials. The LIT-based approach has high reproducibility and reliability because it offers sensitive noncontact temperature measurements and does not require the installation of an external heater. By performing the same measurements and analyses with applying an external magnetic field, the magnetic field and/or magnetization dependences of the Seebeck or Peltier coefficient and thermal conductivity can be determined simultaneously. We demonstrate the validity of this method by using several ferromagnetic metals (Ni, Ni$_{95}$Pt$_{5}$, and Fe) and a nonmagnetic metal (Ti). The proposed method will be useful for materials research in thermoelectrics and spin caloritronics and for investigation of magneto-thermal and magneto-thermoelectric transport properties., 12 pages, 7 figures, 1 table

We phenomenologically calculate the performance of the recently-observed Seebeck-driven transverse thermoelectric generation (STTG) for various systems in terms of the thermopower, power factor, and figure of merit to demonstrate the usefulness of STTG. The STTG system consists of a closed circuit comprising thermoelectric and magnetic materials which exhibit the Seebeck and anomalous Hall effects, respectively. When a temperature gradient is applied to the hybrid system, the Seebeck effect in the thermoelectric material layer generates a longitudinal charge current in the closed circuit and the charge current subsequently drives the anomalous Hall effect in the magnetic material layer. The anomalous Hall voltage driven by the Seebeck effect has a similar symmetry to the transverse thermoelectric conversion based on the anomalous Nernst effect. We find that the thermoelectric properties of STTG can be much better than those of the anomalous Nernst effect by increasing the Seebeck coefficient and anomalous Hall angle of the thermoelectric and magnetic materials, respectively, as well as by optimizing their dimensions. We also formulate the electronic cooling performance in the STTG system, confirming the reciprocal relation for the hybrid transverse thermoelectric conversion., Comment: 7 pages, 4 figures

We have characterized Co$_2$MnGa (CMG) Heusler alloy films grown on Y$_3$Fe$_5$O$_{12}$ (YIG) and Gd$_3$Ga$_5$O$_{12}$ (GGG) substrates at different deposition temperatures and investigated thermo-spin and magneto-thermoelectric conversion properties by means of a lock-in thermography technique. X-ray diffraction, magnetization, and electrical transport measurements show that the deposition at high substrate temperatures induces the crystallized structures of CMG while the resistivity of the CMG films on YIG (GGG) prepared at and above 500 {\deg}C (550 {\deg}C) becomes too high to measure the thermo-spin and magneto-thermoelectric effects due to large roughness, highlighting the difficulty of fabricating highly ordered continuous CMG films on garnet structures. Our lock-in thermography measurements show that the deposition at high substrate temperatures results in an increase in the current-induced temperature change for CMG/GGG and a decrease in that for CMG/YIG. The former indicates the enhancement of the anomalous Ettingshausen effect in CMG through crystallization. The latter can be explained by the superposition of the anomalous Ettingshausen effect and the spin Peltier effect induced by the positive (negative) charge-to-spin conversion for the amorphous (crystallized) CMG films. These results provide a hint to construct spin-caloritronic devices based on Heusler alloys., Comment: 14 pages, 4 figures

The Seebeck and Peltier effects have been widely studied and used in various thermoelectric technologies, including thermal energy harvesting and solid-state heat pumps. However, basic and applied studies on the Thomson effect, another fundamental thermoelectric effect in conductors, are limited despite the fact that the Thomson effect allows electronic cooling through the application of a temperature gradient bias rather than the construction of junction structures. In this article, we report the observation of a giant Thomson effect that appears owing to magnetic phase transitions. The Thomson coefficient of FeRh-based alloys reaches large values approaching $-$1,000 $\mu$VK$^{-1}$ around room temperature because of the steep temperature dependence of the Seebeck coefficient associated with the antiferromagnetic-ferromagnetic phase transition. The Thomson coefficient is several orders of magnitude larger than the Seebeck coefficient of the alloys. Using the active thermography technique, we demonstrate that the Thomson cooling can be much larger than Joule heating in the same material even in a nearly steady state. The operation temperature of the giant Thomson effect in the FeRh-based alloys can be tuned over a wide range by applying an external magnetic field or by slightly changing the composition. Our findings provide a new direction in the materials science of thermoelectrics and pave the way for thermal management applications using the Thomson effect., Comment: 14 pages, 6 figures, 1 table. In Fig. 3, 4, and 5, the definition of the spatial coordinates is changed for easy comparison with previous studies and the arrows showing the charge current directions are reversed to correct a mistake. This revision does not change the conclusion and discussion of the present work and the figures in this version are the same as those in the published version

Non-magnetic materials exhibiting large spin-Hall effect (SHE) are eagerly desired for high-performance spintronic devices. Here, we report that non-equilibrium Cu-Ir binary alloys with compositions beyond the solubility limit are candidates as spin-Hall materials, even though Cu and Ir do not exhibit remarkable SHE themselves. Thanks to non-equilibrium thin film fabrication, the Cu-Ir binary alloys are obtained over a wide composition range even though they are thermodynamically unstable in bulk form. We investigate the SHE of Cu-Ir by exploiting a combinatorial technique based on spin Peltier imaging, and find that the optimum Ir concentration for enhancing SHE is around 25 at.%. We achieve a large spin-Hall angle of 6.29 ± 0.19% for Cu76Ir24. In contrast to Cu-Ir, non-equilibrium Cu-Bi binary alloys do not show remarkable SHE. Our discovery opens a new direction for the exploration of spin-Hall materials. Materials with a large spin-Hall effect are highly desirable for spintronic devices. Here, non-equilibrium thin film synthesis is used to fabricate copper-iridium binary alloys beyond their solubility limit, achieving a large spin-Hall angle of approximately 6% in Cu76Ir24.

The spontaneous order of electric and magnetic dipoles in ferroelectrics and ferromagnets even at high temperatures is both fascinating and useful. Transport of magnetism in the form of spin currents is vigorously studied in spintronics, but the polarization current of the ferroelectric order has escaped attention. We therefore present a time-dependent diffusion theory for heat and polarization transport in a planar ferroelectric capacitor with parameters derived from a one-dimensional phonon model. We predict steady-state Seebeck and transient Peltier effects that await experimental discovery.

A 74-year-old man presented with further treatment for muscle invasive small cell carcinoma of the bladder. After three courses of neoadjuvant chemotherapy with cisplatine + etoposide (EP), total cystectomy was performed. The pathological findings revealed small cell carcinoma of the bladder (ypT2N0M0). Eleven months after the operation, thoracoabdominal computed tomography (CT) showed right pelvic lymph node metastasis. He underwent 9 courses of EP chemotherapy, and everolimus, finally, Amrubicin was administered. Amrubicin might be useful for small cell carcinoma of the bladder.

We report the observation of the higher-order thermoelectric conversion based on a magneto-Thomson effect. By means of thermoelectric imaging techniques, we directly observed the temperature change induced by the Thomson effect in a polycrystalline Bi_{88}Sb_{12} alloy under a magnetic field and found that the magnetically enhanced Thomson coefficient can be comparable to or even larger than the Seebeck coefficient. Our experiments reveal the significant contribution of the higher-order magnetothermoelectric conversion, opening the door to "nonlinear spin caloritronics."

When a temperature gradient is applied to a closed circuit comprising two different conductors, a charge current is generated via the Seebeck effect

The anomalous Ettingshausen effect (AEE) in SmCo$_5$-type permanent magnets has been investigated in the high-temperature range from room temperature to around 600 K. The anomalous Ettingshausen coefficient of the SmCo$_5$ and (SmGd)Co$_5$ magnets monotonically increases with increasing the temperature and shows the similar temperature dependence, while the coefficient of SmCo$_5$ is slightly larger than that of (SmGd)Co$_5$ at high temperatures. The dimensionless figure of merit for AEE in SmCo$_5$ at high temperatures is much greater than the previous record obtained for the anomalous Nernst effect. The observed high-temperature behavior of AEE is discussed based on the first-principles calculations of transverse transport coefficients., Comment: 10 pages, 4 figures

The magnetic skyrmion is a nanoscale topological object characterized by the winding of magnetic moments, appearing in magnetic materials with broken inversion symmetry. Because of its low current threshold for driving the skyrmion motion, they have been intensely studied toward novel storage applications by using electron-beam, X-ray, and visible light microscopies. Here, we demonstrate another imaging method for skyrmions by using spin-caloritronic phenomena, that is, the spin Seebeck and anomalous Nernst effects, as a probe of magnetic texture. We scanned a focused heating spot on a Hall-cross shaped MgO/CoFeB/Ta/W multilayer film and mapped the magnitude as well as the direction of the resultant thermoelectric current due to the spin-caloritronic phenomena. Our experimental and calculation reveal that the characteristic patterns in the thermoelectric signal distribution reflect the skyrmions’ magnetic texture. The thermoelectric microscopy will be a complementary and useful imaging technique for the development of skyrmion devices owing to the unique symmetry of the spin-caloritronic phenomena.

We have studied thermoelectric conversion in all-ferromagnetic Co δ Fe 100 - δ /YIG bilayer junctions as a function of the chemical composition δ . We performed measurements of the transverse thermoelectric voltage upon application of a magnetic field. The voltage measured in the longitudinal spin Seebeck effect configuration shows a sign reversal at δ = 40%, which cannot be explained by the conventional electronic transport, such as the anomalous Nernst and Hall effects in the Co δ Fe 100 - δ layer. Our results suggest a possible role of the sd-type exchange interaction between Co 40 Fe 60 and YIG at the interface as a possible origin for the observed behavior.

This study focuses on the potential of permanent magnets as thermoelectric converters. It is found that a SmCo$_5$-type magnet exhibits the large anomalous Ettingshausen effect (AEE) at room temperature and that its charge-to-heat current conversion coefficient is more than one order of magnitude greater than that of typical ferromagnetic metals. The large AEE is an exclusive feature of the SmCo$_5$-type magnet among various permanent magnets in practical use, which is independent of the conventional performance of magnets based on static magnetic properties. The experimental results show that the large AEE originates from the intrinsic transverse thermoelectric conductivity of SmCo$_5$. This finding makes a connection between permanent magnets and thermal energy engineering, providing the basis for creating "thermoelectric permanent magnets.", 14 pages, 4 figures, 2 supplemental figures, 1 supplemental table

Since the charge current plays a major role in information processing and Joule heating is inevitable in electronic devices, thermal management, i.e., designing heat flows, is required. Here, we report that strain application can change a direction of a heat current generated by magneto-thermoelectric effects. For demonstration, we used metallic magnets in a thin-film form, wherein the anomalous Ettingshausen effect mainly determines the direction of the heat flow. Strain application can alter the magnetization direction owing to the magnetoelastic effect. As a result, the heat current, which is in the direction of the cross product of the charge current and the magnetization vector, can be switched or rotated simply by applying a tensile strain to the metallic magnets. We demonstrate 180° switching and 90° rotation of the heat currents in an in-plane magnetized Ni sample on a rigid sapphire substrate and a perpendicularly magnetized TbFeCo film on a flexible substrate, respectively. An active thermography technique was used to capture the strain-induced change in the heat current direction. The method presented here provides a novel method for controlling thermal energy in electronic devices.

Spin-mediated charge-to-heat current conversion phenomena, i.e., the anomalous Ettingshausen effect (AEE) and the anisotropic magneto-Peltier effect (AMPE), have been investigated in various ferromagnetic Ni-Fe, Ni-Pt, Ni-Pd, and Fe-Pt binary alloys at room temperature. When a charge current is applied to a ferromagnetic conductor, the AMPE modulates the Peltier coefficient depending on the angle between the directions of the charge current and magnetization, while the AEE generates a heat current in the direction perpendicular to both the charge current and magnetization. We observed the strong material dependence of the thermoelectric conversion coefficients and figures of merit of these phenomena. Among the ferromagnetic alloys used in this study, Ni$_{95}$Pt$_{5}$ exhibits the largest AMPE of which the anisotropy of the Peltier coefficient is $\sim 12\%$. In contrast, the magnitude of the AEE signals is moderate in Ni$_{95}$Pt$_{5}$ but largest in Ni$_{75}$Pt$_{25}$ and Ni$_{50}$Fe$_{50}$. We discuss these behaviors by exploring the relations between these charge-to-heat current conversion phenomena and other transport as well as magnetic properties. This systematic study will provide a clue for clarifying the mechanisms of the AMPE and AEE and for enhancing the thermoelectric conversion efficiency of these phenomena., Comment: 21 pages, 14 figures

Transient response of the spin Peltier effect (SPE) in a Pt/yttrium iron garnet junction system has been investigated by means of a lock-in thermoreflectance method. We applied an alternating charge current to the Pt layer to drive SPE through the spin Hall effect, and measured the AC response of the resultant SPE-induced temperature modulation at frequencies ranging from 10 Hz to 1 MHz. We found that the SPE-induced temperature modulation decreases with increasing the frequency when the frequency is >1 kHz. This is a characteristic feature of SPE revealed by the high frequency measurements based on the lock-in thermoreflectance, while previous low frequency measurements showed that the SPE signal is independent of the frequency. We attribute the decrease of the temperature modulation to the length scale of the SPE-induced heat current; by comparing the experimental results with one-dimensional heat conduction calculations, the length scale of SPE is estimated to be 0.94 {\mu}m.

Thermal switching provides an effective way for active heat flow control, which has recently attracted increasing attention in terms of nanoscale thermal management technologies. In magnetic and spintronic materials, the thermal conductivity depends on the magnetization configuration: this is the magneto-thermal resistance effect. Here we show that an epitaxial Cu/Co$_{50}$Fe$_{50}$ multilayer film exhibits giant magnetic-field-induced modulation of the cross-plane thermal conductivity. The magneto-thermal resistance ratio for the Cu/Co$_{50}$Fe$_{50}$ multilayer reaches 150% at room temperature, which is much larger than the previous record high. Although the ratio decreases with increasing the temperature, the giant magneto-thermal resistance effect of ~100% still appears up to 400 K. The magnetic field dependence of the thermal conductivity of the Cu/Co$_{50}$Fe$_{50}$ multilayer was observed to be about twice greater than that of the cross-plane electrical conductivity. The observation of the giant magneto-thermal resistance effect clarifies a potential of spintronic multilayers as thermal switching devices., 23 pages, 3 figures, 5 supplemental figures

We demonstrate non-contact imaging detection of the thermal Hall effect by means of the lock-in thermography with rotationally asymmetric periodic heating. In the lock-in thermography measurements, we applied periodic laser heating in an elliptical pattern to a sample and measured the temperature modulation oscillating at the same frequency as the heating under a magnetic field. From the magnetic field dependence of the elliptical heating pattern, the temperature modulation due to the thermal Hall effect can be extracted. We confirm the validity of this method by detecting a signature pattern specific to the thermal Hall effect in a Bi slab at room temperature.

Spin currents can be carried by electrons and by magnons. Experiments now show that, in one-dimensional spin chains, spin currents can also be carried by particle-like excitations known as spinons. Quantum spin fluctuation in a low-dimensional or frustrated magnet breaks magnetic ordering while keeping spin correlation1. Such fluctuation has been a central topic in magnetism because of its relevance to high-Tc superconductivity2 and topological states3. However, utilizing such spin states has been quite difficult. In a one-dimensional spin-1/2 chain, a particle-like excitation called a spinon is known to be responsible for spin fluctuation in a paramagnetic state. Spinons behave as a Tomonaga–Luttinger liquid at low energy, and the spin system is often called a quantum spin chain4. Here we show that a quantum spin chain generates and carries spin current, which is attributed to spinon spin current. This is demonstrated by observing an anisotropic negative spin Seebeck effect5,6,7,8,9,10 along the spin chains in Sr2CuO3. The results show that spin current can flow even in an atomic channel owing to long-range spin fluctuation.

The second-order conventional and first-order inverse magnetocaloric effects (MCEs) in Ni–Mn-based quaternary Heusler alloys have been systematically investigated by means of the lock-in thermography technique, which enables the direct measurement of the MCE-induced temperature change in a periodic magnetic field. Through systematic measurements of the temperature dependence of the MCE signals, the tuning of the conventional and inverse MCEs with temperature for the same Heusler alloys has been demonstrated, where the phase transitions responsible for the MCEs are clearly distinguished. The lock-in thermography measurements show that some Ni–Mn-based Heusler alloys exhibit much smaller temperature changes due to the inverse MCEs in the periodic field as compared to the conventional MCEs, even though they exhibit a larger magnetic entropy change across the first-order transition responsible for the inverse MCEs. We discuss the origin of this behavior in terms of the field-induced entropy change and thermal hysteresis of the alloys. These findings will be useful not only in accelerating the optimization of inverse MCE materials but also in understanding the mechanism of the MCEs.

We demonstrate the enhancement of charge-to-spin current conversion by a ferromagnet/paramagnet interface. The enhancement is confirmed by comparing the spin Peltier effect (SPE) between Ni/Pt/yttrium-iron-garnet (YIG) and Pt/YIG hybrid structures, where the SPE signal is proportional to the spin current generated in the Ni/Pt or Pt layer. The SPE signal normalized by charge current density for the Ni/Pt/YIG system increases by 65% compared to the Pt/YIG system, which cannot be explained by other thermoelectric and thermo-spin effects. This result suggests the presence of additive charge-to-spin current conversion at the Ni/Pt interface, providing simple ways to improve spin-injection efficiency.

Conversion between spin and charge currents is essential in spintronics, since it enables spin-orbit-torque magnetization switching, spin-current-driven thermoelectric generation, and nano-scale thermal energy control. To realize efficient spin-charge conversion, a variety of mechanisms, including spin Hall effects, Rashba-Edelstein effects, and spin-momentum locking in topological insulators, have been investigated and more comprehensive material exploration is necessary. Here we demonstrate high-throughput screening of spin-charge conversion materials by means of the spin Peltier effect (SPE). This is enabled by combining recently-developed SPE-imaging techniques with combinatorial materials science; using a composition-spread alloy film formed on a magnetic insulator, we observe the SPE-induced temperature change due to the spin Hall effect and obtain a continuous mapping of its composition dependence from the single sample. The distribution of the SPE signals reflects local spin-charge conversion capability in the alloy owing to unique heat-generation nature of the SPE. This combinatorial approach will accelerate materials research towards high-performance spintronic devices.