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To utilize half-metallic Heusler alloys in practical spintronic devices, such as magnetic sensors and magnetic memories, the key is to realize highly textured and structurally ordered polycrystalline thin films. In this study, we fabricated polycrystalline Co2FeGa0.5Ge0.5 (CFGG) Heusler alloy films deposited on a [001]-oriented Ag buffer layer, which was achieved by introducing N2 into Ar during the sputtering process, on a thermally oxidized Si substrate. We obtained strongly [001]-oriented CFGG films with B2 ordering and a high saturation magnetization close to the theoretical value, which can provide highly spin-polarized electric and spin current sources in spintronic devices with industrial viability., Comment: 16 papers, 5 figures

Thermal conductivity, a fundamental parameter characterizing thermal transport in solids, is typically determined by electron and phonon transport. Although other transport properties including electrical conductivity and thermoelectric conversion coefficients have material-specific values, it is known that thermal conductivity can be modulated artificially via phonon engineering techniques. Here, we demonstrate another way of artificially modulating the heat conduction in solids: magnonic thermal transport engineering. The time-domain thermoreflectance measurements using ferromagnetic metal/insulator junction systems reveal that the thermal conductivity of the ferromagnetic metals and interfacial thermal conductance vary significantly depending on the spatial distribution of nonequilibrium spin currents. Systematic measurements of the thermal transport properties with changing the boundary conditions for spin currents show that the observed thermal transport modulation stems from magnon origin. This observation unveils that magnons significantly contribute to the heat conduction even in ferromagnetic metals at room temperature, upsetting the conventional wisdom that the thermal conductivity mediated by magnons is very small in metals except at low temperatures. The magnonic thermal transport engineering offers a new principle and method for active thermal management.

Recent advances in the study of materials with topological electronic band structures have revealed magnetic materials exhibiting giant anomalous Hall effects (AHE). The giant AHE has not only attracted the research interest in its mechanism but also opened up the possibility of practical application in magnetic sensors. In this article, we describe simulation-based investigations of AHE magnetic sensors for the applications to read head sensors (readers) of hard disk drives. With the shrinking of magnetic recording patterns, the reader technology, which currently uses multilayer-based tunnel magnetoresistance (TMR) devices, is associated with fundamental challenges, such as insufficient spatial resolution and signal-to-noise ratio (SNR) in sensors with dimensions below 20 nm. The structure of an AHE-based device composed of a single ferromagnetic material is advantageous for magnetic sensors with nanoscale dimensions. We found that AHE readers using topological ferromagnets with giant AHE, such as Co2MnGa, can achieve a higher SNR than current TMR readers. The higher SNR originates from the large output signal of the giant AHE as well as from the reduced thermal magnetic noise, which is the dominant noise in TMR readers. We highlight a major challenge in the development of AHE readers: the reduction in the output signal due to the shunting of the bias current and the leakage of the Hall voltage through the soft magnetic shields surrounding the AHE reader. We propose reader structures that overcome this challenge. Finally, we discuss the scope for future research to realize AHE readers., Comment: Revised version after peer-review

Topological quantum materials can exhibit unconventional surface states and anomalous transport properties. Still, their applications in spintronic devices are restricted as they require the growth of high-quality thin films with bulk-like properties. Here, we study 10--30 nm thick epitaxial ferromagnetic Co$_{\rm 2}$MnGa films with high structural order and very high values of the anomalous Hall conductivity, $\sigma_{\rm xy}=1.35\times10^{5}$ $\Omega^{-1} m^{-1}$ and the anomalous Hall angle, $\theta_{\rm H}=15.8\%$, both comparable to bulk values. We observe a dramatic crystalline orientation dependence of the Gilbert damping constant of a factor of two and a giant intrinsic spin Hall conductivity, $\mathit{\sigma_{\rm SHC}}=(6.08\pm 0.02)\times 10^{5}$ ($\hbar/2e$) $\Omega^{-1} m^{-1}$, an order of magnitude higher than literature values of multilayer Co$_{\rm 2}$MnGa stacks [1-3] and single-layer Ni, Co, Fe [4], and Ni$_{\rm 80}$Fe$_{\rm 20}$~[4,5]. As a consequence, spin-orbit-torque driven auto-oscillations of a 30 nm thick magnetic film are observed for the first time, at an ultralow threshold current density of $J_{th}=6.2\times10^{11}$ $Am^{-2}$. Theoretical calculations of the intrinsic spin Hall conductivity, originating from a strong Berry curvature, corroborate the results and yield values comparable to the experiment. Our results open up for the design of spintronic devices based on single layers of magnetic topological quantum materials., Comment: 19 pages

We develop a high-throughput method for measuring the composition dependence of magnetoresistance (MR) and spin-transfer-torque (STT) effects in current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices and report its application to the CoFe system. The method is based on the use of composition-gradient films deposited by combinatorial sputtering. This structure allows the fabrication of devices with different compositions on a single substrate, drastically enhancing the throughput in investigating composition dependence. We fabricated CPP-GMR devices on a single GMR film consisting of a Co$_{x}$Fe$_{1-x}$ (0 $\le$ $\textit{x}$ $\le$ 1) composition-gradient layer, a Cu spacer layer, and a NiFe layer. The MR ratio obtained from resistance-field measurements exhibited the maximum in the broad Co concentration range of 0.3 $\le$ $\textit{x}$ $\le$ 0.65. In addition, the STT efficiency was estimated from the current to induce magnetization reversal of the NiFe layer by spin injection from the Co$_{x}$Fe$_{1-x}$ layer. The STT efficiency was also the highest around the same Co concentration range as for the MR ratio, and this correlation was theoretically explained by the change in the spin polarization of the Co$_{x}$Fe$_{1-x}$ layer. The results revealed the Co$_{x}$Fe$_{1-x}$ composition range suitable for spintronic applications, demonstrating the advantages of the developed method., Comment: 19 pages, 5 figures

The Seebeck-driven transverse thermoelectric generation in magnetic/thermoelectric hybrid materials (STTG) has been investigated in all-bulk hybrid materials. The transverse thermopower in a ferromagnetic Co$_2$MnGa/thermoelectric $n$-type Si hybrid bulk material with the adjusted dimensions reaches 16.0 $\mu$V/K at room temperature with the aid of the STTG contribution, which is much larger than the anomalous Nernst coefficient of the Co$_2$MnGa slab (6.8 $\mu$V/K). Although this transverse thermopower is smaller than the value for previously reported thin-film-based hybrid materials, the hybrid bulk materials exhibit much larger electrical power owing to their small internal resistance. This demonstration confirms the validity of STTG in bulk materials and clarifies its potential as a thermal energy harvester., Comment: 12 pages, 4 figures, 1 table

Despite the usefulness of the anomalous Nernst conductivity ($\alpha^{A}_{xy}$) for studying electronic band structures and exploring magnetic materials with large transverse thermopower, there has not been a straightforward way to obtain $\alpha^{A}_{xy}$ in the experiment. Here, we propose a simple and versatile method enabling direct electrical probing of $\alpha^{A}_{xy}$, which is realized by creating a closed circuit consisting of a target magnetic material and a non-magnetic conductor. This method was experimentally demonstrated on a thin film of magnetic Weyl semimetal Co$_{2}$MnGa, where the closed circuit was formed simply by connecting both ends of the Co$_{2}$MnGa film with a Au wire. A good approximation of $\alpha^{A}_{xy}$ was obtained in a wide temperature range, validating the proposed method and exhibiting its potential for aiding the further development of topological materials science and transverse thermoelectrics., Comment: 7 pages, 5 figures

An unconventional approach to enhance the transverse thermopower by combining magnetic and thermoelectric materials, namely the Seebeck-driven transverse thermoelectric generation (STTG), has been proposed and demonstrated recently. Here, we improve on the previously used sample structure and achieve large transverse thermopower over 40 $\mu$V K$^{-1}$ due to STTG in on-chip devices. We deposited polycrystalline Fe-Ga alloy films directly on n-type Si substrates, where Fe-Ga and Si serve as the magnetic and thermoelectric materials, respectively. Using microfabrication, contact holes were created through the SiO$_{x}$ layer at the top of Si to electrically connect the Fe-Ga film with the Si substrate. These thin devices with simple structure clearly exhibited enhancement of transverse thermopower due to STTG, and the obtained values agreed well with the estimation over a wide range of the size ratio between the Fe-Ga film and the Si substrate., Comment: 8 pages, 7 figures

Transverse thermoelectric generation using magnetic materials is essential to develop active thermal engineering technologies, for which the improvements of not only the thermoelectric output but also applicability and versatility are required. In this study, using combinatorial material science and lock-in thermography technique, we have systematically investigated the transverse thermoelectric performance of Sm-Co-based alloy films. The high-throughput material investigation revealed the best Sm-Co-based alloys with the large anomalous Nernst effect (ANE) as well as the anomalous Ettingshausen effect (AEE). In addition to ANE/AEE, we discovered unique and superior material properties in these alloys: the amorphous structure, low thermal conductivity, and large in-plane coercivity and remanent magnetization. These properties make it advantageous over conventional materials to realize heat flux sensing applications based on ANE, as our Sm-Co-based films can generate thermoelectric output without an external magnetic field. Importantly, the amorphous nature enables the fabrication of these films on various substrates including flexible sheets, making the large-scale and low-cost manufacturing easier. Our demonstration will provide a pathway to develop flexible transverse thermoelectric devices for smart thermal management., Comment: 40 pages in total, 10 main figures, 1 graphical abstract, 3 supplementary 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

The negative sign of the anomalous Nernst thermopower ($S_\text{ANE}$) observed in Mn-Ga ordered alloys is an attractive property for thermoelectric applications exploiting the anomalous Nernst effect (ANE); however, its origin has not been clarified. In this study, to gain insight into the negative $S_\text{ANE}$, we prepared epitaxial thin films of Mn$_{x}$Ga$_{100-x}$ with $x$ ranging from 56.2 to 71.7, and systematically investigated the structural, magnetic, and transport properties including the anomalous Hall effect (AHE) and the ANE. The measured $S_\text{ANE}$ is negative for all samples and shows close to one order of magnitude difference among different compositions. Together with the measured transport properties, we were able to separate the two different contributions of the ANE, i.e., one originating from the transverse thermoelectric coefficient ($\alpha_{xy}$), and the other one originating from the AHE acting on the longitudinal carrier flow induced by the Seebeck effect. Both contributions are found to be negative for all samples, while the experimentally obtained negative $\alpha_{xy}$ exhibits a monotonic increase towards zero with increasing $x$, which is consistent with the tendency indicated by first-principles calculations. Our results show that the large difference in the negative $S_\text{ANE}$ is mostly attributed to $\alpha_{xy}$, and thus shed light on further enhancement of the ANE in Mn-based ordered alloys., Comment: 13 pages, 5 figures

A tuning of Fermi level (E$_F$) near Weyl points is one of the promising approaches to realize large anomalous Nernst effect (ANE). In this work, we introduce an efficient approach to tune E$_F$ for the Co$_2$MnAl Weyl semimetal through a layer-by-layer combinatorial deposition of Co$_2$MnAl$_{1-x}$Si$_x$ (CMAS) thin film. A single-crystalline composition-spread film with x varied from 0 to 1 was fabricated. The structural characterization reveals the formation of single-phase CMAS alloy throughout the composition range with a gradual improvement of L2$_1$ order with x similar to the co-sputtered single layered film, which validates the present fabrication technique. Hard X-ray photoemission spectroscopy for the CMAS composition-spread film directly confirmed the rigid band-like E$_F$ shift of approximately 0.40 eV towards the composition gradient direction from x = 0 to 1. The anomalous Ettingshausen effect (AEE), the reciprocal of ANE, has been measured for whole x range using a single strip along the composition gradient using the lock-in thermography technique. The similarity of the x dependence of observed AEE and ANE signals clearly demonstrates that the AEE measurement on the composition spread film is an effective approach to investigate the composition dependence of ANE of Weyl semimetal thin films and realize the highest performance without fabricating several films, which will accelerate the research for ANE-based energy harvesting, Comment: total 29 pages, 6 main figures, 3 supplementary figures, 1 supplementary table

The transverse thermoelectric effect refers to the conversion of a temperature gradient into a transverse charge current, or vice versa, which appears in a conductor under a magnetic field or in a magnetic material with spontaneous magnetization. Among such phenomena, the anomalous Nernst effect in magnetic materials has been receiving increased attention from the viewpoints of fundamental physics and thermoelectric applications owing to the rapid development of spin caloritronics and topological materials science. In this research trend, a conceptually different transverse thermoelectric conversion phenomenon appearing in thermoelectric/magnetic hybrid materials has been demonstrated, enabling the generation of a large transverse thermopower. Here, we review the recent progress in fundamental and applied studies on the transverse thermoelectric generation using magnetic materials. We anticipate that this perspective will further stimulate research activities on the transverse thermoelectric generation and lead to the development of next-generation thermal energy harvesting and heat-flux sensing technologies., Comment: 18 pages, 5 figures

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

Inverse Heusler alloy Mn2CoAl thin films, known as a spin-gapless semiconductor (SGS), grown by three different methods: ultra-high vacuum magnetron spattering, Ar-ion beam assisted sputtering, and molecular beam epitaxy, are investigated by comparing their electric transport properties, microstructures and atomic-level structures. Of the samples, the Mn2CoAl thin film grown by MBE consists of Mn- and Co-rich phases, the structures of which are determined to be the L21B-type and disordered L21-type, respectively, according to anomalous XRD analysis. None of them forms the XA-type structure expected for SGS Heusler alloy, although they all show SGS characteristics. We suggest, to validate SGS characteristics, it is necessary to extract not only magnetic and electric transport properties but also information about microstructures and atomic-scale structures of the films including defects such as atomic swap.

Ferrimagnetic Mn$_4$N is a promising material for heat flux sensors based on the anomalous Nernst effect (ANE) because of its sizable uniaxial magnetic anisotropy ($K_{\rm u}$) and low saturation magnetization ($M_{\rm s}$). We experimentally and theoretically investigated the ANE and anomalous Hall effect in sputter-deposited Mn$_4$N films. It was revealed that the observed negative anomalous Hall conductivity ($\sigma_{xy}$) could be explained by two different coexisting magnetic structures, that is, a dominant magnetic structure with high $K_{\rm u}$ contaminated by another structure with negligible $K_{\rm u}$ owing to an imperfect degree of order of nitrogen. The observed transverse thermoelectric power ($S_{\rm ANE}$) of $+0.5\, \mu{\rm V/K}$ at $300\, {\rm K}$ gave a transverse thermoelectric coefficient ($\alpha_{xy}$) of $+0.34\, {\rm A/(m \cdot K)}$, which was smaller than the value predicted from first-principles calculation. The interpretation for $\alpha_{xy}$ based on the first-principles calculations led us to conclude that the realization of single magnetic structure with high $K_{\rm u}$ and optimal adjustment of the Fermi level are promising approaches to enhance $S_{\rm ANE}$ in Mn$_4$N through the sign reversal of $\sigma_{xy}$ and the enlargement of $\alpha_{xy}$ up to a theoretical value of $1.77\, {\rm A/(m \cdot K)}$., Comment: 28 pages, 6 figures, 1 table (including supplemental material)

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., Comment: 23 pages, 3 figures, 5 supplemental figures

Voltage-controlled magnetic anisotropy (VCMA) offers an emerging approach to realize energy-efficient magnetization switching in spintronic devices such as magnetic random access memories (MRAMs). Here, we show that manipulating the condensed states, i.e., introducing quantum well (QW) can significantly influence the VCMA in a Cr/Fe-QW/MgAl2O4 based magnetic tunnel junction (MTJ). Only for the MTJ with an even number of Fe atomic layers, we observed a novel A-shaped VCMA curve for a particular QW state, where magnetic anisotropy energy (MAE) reaches a local maximum at zero bias and reduces when applying both positive and negative bias, i.e., a novel bi-polar VCMA effect. Our ab initio calculations demonstrate that the QW states give an additional contribution to perpendicular magnetic anisotropy (PMA), which can explain not only the A-shaped VCMA but also the Fe-layer-number parity dependence of VCMA. The present study suggests that the QW-modulated VCMA should open a new pathway to design VCMA-assisted MRAM., Comment: 26 pages, 8 figures

Weyl semimetals are characterized by the presence of massless band dispersion in momentum space. When a Weyl semimetal meets magnetism, large anomalous transport properties emerge as a consequence of its topological nature. Here, using $in-situ$ spin- and angle-resolved photoelectron spectroscopy combined with $ab\ initio$ calculations, we visualize the spin-polarized Weyl cone and flat-band surface states of ferromagnetic Co$_2$MnGa films with full remanent magnetization. We demonstrate that the anomalous Hall and Nernst conductivities systematically grow when the magnetization-induced massive Weyl cone at a Lifshitz quantum critical point approaches the Fermi energy, until a high anomalous Nernst thermopower of $\sim 6.2$ $\rm \mu V K^{-1}$ is realized at room temperature. Given this topological quantum state and full remanent magnetization, Co$_2$MnGa films are promising for realizing high efficiency heat flux and magnetic field sensing devices operable at room temperature and zero-field., Comment: 25 pages, 5 figures, 1 table

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.", Comment: 14 pages, 4 figures, 2 supplemental figures, 1 supplemental table

We derive a simple relational expression between the spin polarization ratio of resistivity, $P_\rho$, and the anisotropic magnetoresistance ratio $\Delta \rho/\rho$, and that between the spin polarization ratio of the density of states at the Fermi energy, $P_{\rm DOS}$, and $\Delta \rho/\rho$ for nearly half-metallic ferromagnets. We find that $P_\rho$ and $P_{\rm DOS}$ increase with increasing $|\Delta \rho/\rho|$ from 0 to a maximum value. In addition, we roughly estimate $P_\rho$ and $P_{\rm DOS}$ for a Co$_2$FeGa$_{0.5}$Ge$_{0.5}$ Heusler alloy by substituting its experimentally observed $\Delta \rho/\rho$ into the respective expressions., Comment: 10 pages, 3 figures, 2 tables, to be published in Jpn. J. Appl. Phys

The spin Hall effect allows generation of spin current when charge current is passed along materials with large spin orbit coupling. It has been recently predicted that heat current in a non-magnetic metal can be converted into spin current via a process referred to as the spin Nernst effect. Here we report the observation of the spin Nernst effect in W. In W/CoFeB/MgO heterostructures, we find changes in the longitudinal and transverse voltages with magnetic field when temperature gradient is applied across the film. The field-dependence of the voltage resembles that of the spin Hall magnetoresistance. A comparison of the temperature gradient induced voltage and the spin Hall magnetoresistance allows direct estimation of the spin Nernst angle. We find the spin Nernst angle of W to be similar in magnitude but opposite in sign with its spin Hall angle. Interestingly, under an open circuit condition, such sign difference results in spin current generation larger than otherwise. These results highlight the distinct characteristics of the spin Nernst and spin Hall effects, providing pathways to explore materials with unique band structures that may generate large spin current with high efficiency.

We model the charge, spin, and heat currents in ferromagnetic metal$|$normal metal$|$normal metal trilayer structures in the two current model, taking into account bulk and interface thermoelectric properties as well as Joule heating. Results include the temperature distribution as well as resistance-current curves that reproduce the observed shifted parabolic characteristics. Thin tunneling barriers can enhance the apparent Peltier cooling. The model agrees with experimental results for wide multilayer pillars, but the giant effects observed for diameters $\lesssim 100\,$nm are still under discussion., Comment: 11 pages, 7 figures