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Claudia Felser - One of the best experts on this subject based on the ideXlab platform.
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anomalous nernst effect beyond the magnetization scaling relation in the ferromagnetic Heusler Compound co2mnga
Npg Asia Materials, 2019Co-Authors: Satya N. Guin, Chandra Shekhar, Kaustuv Manna, Jonathan Noky, Sarah J. Watzman, Nitesh Kumar, Walter Schnelle, Yan Sun, Johannes Gooth, Claudia FelserAbstract:Applying a temperature gradient in a magnetic material generates a voltage that is perpendicular to both the heat flow and the magnetization. This phenomenon is the anomalous Nernst effect (ANE), which was long thought to be proportional to the value of the magnetization. However, more generally, the ANE has been predicted to originate from a net Berry curvature of all bands near the Fermi level (EF). Subsequently, a large anomalous Nernst thermopower ( $${\boldsymbol{S}}_{{\boldsymbol{yx}}}^{\boldsymbol{A}}$$ ) has recently been observed in topological materials with no net magnetization but a large net Berry curvature [Ωn(k)] around EF. These experiments clearly fall outside the scope of the conventional magnetization model of the ANE, but a significant question remains. Can the value of the ANE in topological ferromagnets exceed the highest values observed in conventional ferromagnets? Here, we report a remarkably high $${\boldsymbol{S}}_{{\boldsymbol{yx}}}^{\boldsymbol{A}}$$ -value of ~6.0 µV K−1 in the ferromagnetic topological Heusler Compound Co2MnGa at room temperature, which is approximately seven times larger than any anomalous Nernst thermopower value ever reported for a conventional ferromagnet. Combined electrical, thermoelectric, and first-principles calculations reveal that this high-value of the ANE arises from a large net Berry curvature near the Fermi level associated with nodal lines and Weyl points. Thermoelectric devices that convert heat into electricity may benefit from the unusual temperature sensitivity of cobalt–manganese–gallium (Co2MnGa) ferromagnets. When one end of a magnetized metal is made hot and the other cold, redistribution of electrons creates an electric voltage perpendicular to the temperature gradient. Satya N. Guin from the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany, and colleagues now report how certain class of material can boost the electrical power produced from “waste heat” source using transverse thermoelectric effect. When the team applied magnetic fields to Co2MnGa and characterized its transverse electrical response to temperature gradient, they saw voltage generation several times higher than expected. Computer simulations indicated that the crystal geometry distorted the energy levels available to electron making it easier for electrons to move when thermally excited. We report a high anomalous Nernst thermopower ( $$S_{yx}^A$$ ) -value of ~6.0 µV K−1 at room temperature in the ferromagnetic topological Heusler Compound Co2MnGa. The measured value is seven-times larger than any anomalous Nernst thermopower value ever reported for a conventional ferromagnet. The high anomalous Nernst effect originates from a large net Berry curvature near the Fermi level associated with nodal lines and Weyl points.
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anisotropic topological hall effect with real and momentum space berry curvature in the antiskrymion hosting Heusler Compound mn 1 4 ptsn
Physical Review B, 2019Co-Authors: Praveen Vir, Chandra Shekhar, Nitesh Kumar, Yan Sun, Jacob Gayles, A S Sukhanov, Francoise Damay, J Kubler, Claudia FelserAbstract:The topological Hall effect (THE) is one of the key signatures of topologically nontrivial magnetic spin textures, wherein electrons feel an additional transverse voltage to the applied current. The magnitude of THE is often small compared to the anomalous Hall effect. Here, we find a large THE of $0.9\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{\ensuremath{\Omega}}\phantom{\rule{0.16em}{0ex}}\mathrm{cm}$ that is of the same order of the anomalous Hall effect in the single-crystalline antiskyrmion-hosting Heusler Compound ${\mathrm{Mn}}_{1.4}\mathrm{PtSn}$, a noncentrosymmetric tetragonal Compound. The THE is highly anisotropic and survives in the whole temperature range where the spin structure is noncoplanar (170 K). The THE is zero above the spin reorientation transition temperature of 170 K, where the magnetization will have a collinear and ferromagnetic alignment. The large value of the THE entails a significant contribution from the momentum-space Berry curvature along with real-space Berry curvature, which has never been observed earlier.
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anomalous nernst effect beyond the magnetization scaling relation in the ferromagnetic Heusler Compound co _2 mnga
arXiv: Materials Science, 2018Co-Authors: Satya N. Guin, Chandra Shekhar, Kaustuv Manna, Jonathan Noky, Sarah J. Watzman, Nitesh Kumar, Walter Schnelle, Yan Sun, Johannes Gooth, Claudia FelserAbstract:Applying a temperature gradient in a magnetic material generates a voltage that is perpendicular to both the heat flow and the magnetization. This is the anomalous Nernst effect (ANE) which was thought to be proportional to the value of the magnetization for a long time. However, more generally, the ANE has been predicted to originate from a net Berry curvature of all bands near the Fermi level. Subsequently, a large anomalous Nernst thermopower has recently been observed in topological materials with no net magnetization but large net Berry curvature around E$_F$. These experiments clearly fall outside the scope of the conventional magnetization-model of the ANE, but a significant question remains: Can the value of the ANE in topological ferromagnets exceed the highest values observed in conventional ferromagnets? Here, we report a remarkably high anomalous Nernst thermopower value of ~6.0 \mu V/K at 1 T in the ferromagnetic topological Heusler Compound Co$_2$MnGa at room temperature, which is around 7-times larger than any anomalous Nernst thermopower value ever reported for a conventional ferromagnet. Combined electrical, thermoelectric and first-principles calculations reveal that this high value of the ANE arises from a large net Berry curvature near the Fermi level associated with nodal lines and Weyl points.
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Weyl points in the ferromagnetic Heusler Compound Co2MnAl
EPL (Europhysics Letters), 2016Co-Authors: Jurgen Kubler, Claudia FelserAbstract:The anomalous Hall conductivity (AHC) in some ferromagnetic and antiferromagnetic Heusler Compounds was theoretically and experimentally found to be exceptionally large. For the case of ferromagnetic Co2MnAl we here argue that the large AHC is connected with the appearance of Weyl points near the Fermi energy. We find four Weyl points slightly above the Fermi edge. We describe our analysis for a magnetization being in the (110)-direction. For the possible (100)-direction we find at least four Weyl points, too. We predict that Co2MnGa also possesses Weyl points near or at the Fermi energy.
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Tunable damping in the Heusler Compound Co2-xIrxMnSi
Physical Review B, 2016Co-Authors: Albrecht Köhler, Lukas Wollmann, Daniel Ebke, Stanislav Chadov, Christian Kaiser, Zhitao Diao, Yuankai Zheng, Qunwen Leng, Claudia FelserAbstract:Here we report on the realization of tuning the intrinsic damping in the half-metallic Heusler Compound Co2MnSi by substituting Co by Ir. The work includes theoretical calculations and experimental measurements on bulk and thin films samples. Control of damping is to remove unwanted magnetization motion and suppress signal echoes through uncontrolled precession of the magnetization for future implementation of this material into, e.g., current perpendicular plane-giant-magnetoresistance sensors. Density functional calculations revealed stable magnetization and increasing damping parameter with Iridium concentration, whereas the half metallicity could be retained. The calculations are consistent with experimental results from bulk and thin film samples of this report and elucidate the linear dependence of the Gilbert damping parameter on the substituent concentration. This report again demonstrates the inherent tunability of Heusler Compounds, which constitutes a pivotal feature of this material class
Kohei Hamaya - One of the best experts on this subject based on the ideXlab platform.
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Spin transport and accumulation in n+-Si using Heusler Compound Co2FeSi/MgO tunnel contacts
Applied Physics Letters, 2015Co-Authors: Mizue Ishikawa, Kohei Hamaya, Hideyuki Sugiyama, Tomoaki Inokuchi, Yoshiaki SaitoAbstract:We investigate spin transport and accumulation in n+-Si using Heusler Compound Co2FeSi/MgO/Si on insulator (SOI) devices. The magnitudes of the non-local four- and three-terminal Hanle effect signals when using Heusler Compound Co2FeSi/MgO/SOI devices are larger than when using CoFe/MgO/SOI devices, whereas the preparation methods of MgO layers on SOI are exactly same in both devices. Different bias voltage dependencies on the magnitude of spin accumulation signals are also observed between these devices. Especially, Co2FeSi/MgO/SOI devices show large spin accumulation signals compared with CoFe/MgO/SOI devices in the low bias voltage region less than ∼1000 mV in which the increase of the spin polarization is expected from the estimation of the density of states in Heusler Compound Co2FeSi and CoFe under spin extraction conditions. These results indicate that the species of ferromagnetic material definitely affects the magnitude and behavior of the spin signals. The use of highly polarized ferromagnets su...
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Room-temperature generation of giant pure spin currents using epitaxial Co_2FeSi spin injectors
NPG Asia Materials, 2012Co-Authors: Takashi Kimura, Masanobu Miyao, Shinya Yamada, Naoki Hashimoto, Kohei HamayaAbstract:Spintronics: Current generationTakashi Kimura, Kohei Hamaya and co-workers have generated large pure spin currents at room temperature, with high efficiency. Spintronic devices, which use the spin of electrons as well as their charge, promise to be faster and less power-consuming than traditional charge-based electronic ones. A pure spin current — a flow that is not accompanied by charge current — seems to be a promising way to write information for such devices. However, although ‘spin injectors’ capable of creating such currents have been developed, their efficiency has generally remained too low for practical applications. Now, Kimura, Hamaya and colleagues have significantly improved this efficiency by using a highly ordered cobalt-iron-silicon ‘Heusler’ Compound with high spin polarization. These findings highlight the potential of Heusler Compounds as spin injectors, and move the construction of functional spintronic devices one step forward.Heusler Compound spin injector with a high spin polarization dramatically improves the generation efficiency of the pure spin current compared with a conventional ferromagnetic metal.AbstractThe generation, manipulation and detection of a pure spin current (i.e., the flow of spin angular momentum without a charge current) are prospective approaches for realizing next-generation spintronic devices with ultra-low electric power consumption. Conventional ferromagnetic electrodes such as Co and NiFe have been utilized as spin injectors to generate pure spin currents in nonmagnetic channels. However, the generation efficiency of pure spin currents is extremely low at room temperature, giving rise to a serious obstacle for device applications. Here we demonstrate the generation of giant pure spin currents at room temperature in lateral spin valve devices with a highly ordered Heusler-Compound Co_2FeSi (CFS) spin injector. The generation efficiency of pure spin currents from the CFS spin injectors is 10 times greater than that of the NiFe injectors, indicating that Heusler Compound spin injectors with high spin polarization enable us to materialize a high-performance lateral spin device. The present study is a technological jump in spintronics, and indicates the great potential of ferromagnetic Heusler Compounds with half metallicity for generating pure spin currents.
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Room-temperature generation of giant pure spin currents using epitaxial Co_2FeSi spin injectors
NPG Asia Materials, 2012Co-Authors: Takashi Kimura, Masanobu Miyao, Shinya Yamada, Naoki Hashimoto, Kohei HamayaAbstract:The generation, manipulation and detection of a pure spin current (i.e., the flow of spin angular momentum without a charge current) are prospective approaches for realizing next-generation spintronic devices with ultra-low electric power consumption. Conventional ferromagnetic electrodes such as Co and NiFe have been utilized as spin injectors to generate pure spin currents in nonmagnetic channels. However, the generation efficiency of pure spin currents is extremely low at room temperature, giving rise to a serious obstacle for device applications. Here we demonstrate the generation of giant pure spin currents at room temperature in lateral spin valve devices with a highly ordered Heusler-Compound Co_2FeSi (CFS) spin injector. The generation efficiency of pure spin currents from the CFS spin injectors is 10 times greater than that of the NiFe injectors, indicating that Heusler Compound spin injectors with high spin polarization enable us to materialize a high-performance lateral spin device. The present study is a technological jump in spintronics, and indicates the great potential of ferromagnetic Heusler Compounds with half metallicity for generating pure spin currents. Takashi Kimura, Kohei Hamaya and co-workers have generated large pure spin currents at room temperature, with high efficiency. Spintronic devices, which use the spin of electrons as well as their charge, promise to be faster and less power-consuming than traditional charge-based electronic ones. A pure spin current — a flow that is not accompanied by charge current — seems to be a promising way to write information for such devices. However, although ‘spin injectors’ capable of creating such currents have been developed, their efficiency has generally remained too low for practical applications. Now, Kimura, Hamaya and colleagues have significantly improved this efficiency by using a highly ordered cobalt-iron-silicon ‘Heusler’ Compound with high spin polarization. These findings highlight the potential of Heusler Compounds as spin injectors, and move the construction of functional spintronic devices one step forward. Heusler Compound spin injector with a high spin polarization dramatically improves the generation efficiency of the pure spin current compared with a conventional ferromagnetic metal.
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room temperature generation of giant pure spin currents using epitaxial co2fesi spin injectors
Npg Asia Materials, 2012Co-Authors: Takashi Kimura, Masanobu Miyao, Kohei Hamaya, Shinya Yamada, Naoki HashimotoAbstract:The generation, manipulation and detection of a pure spin current (i.e., the flow of spin angular momentum without a charge current) are prospective approaches for realizing next-generation spintronic devices with ultra-low electric power consumption. Conventional ferromagnetic electrodes such as Co and NiFe have been utilized as spin injectors to generate pure spin currents in nonmagnetic channels. However, the generation efficiency of pure spin currents is extremely low at room temperature, giving rise to a serious obstacle for device applications. Here we demonstrate the generation of giant pure spin currents at room temperature in lateral spin valve devices with a highly ordered Heusler-Compound Co2FeSi (CFS) spin injector. The generation efficiency of pure spin currents from the CFS spin injectors is 10 times greater than that of the NiFe injectors, indicating that Heusler Compound spin injectors with high spin polarization enable us to materialize a high-performance lateral spin device. The present study is a technological jump in spintronics, and indicates the great potential of ferromagnetic Heusler Compounds with half metallicity for generating pure spin currents. Takashi Kimura, Kohei Hamaya and co-workers have generated large pure spin currents at room temperature, with high efficiency. Spintronic devices, which use the spin of electrons as well as their charge, promise to be faster and less power-consuming than traditional charge-based electronic ones. A pure spin current — a flow that is not accompanied by charge current — seems to be a promising way to write information for such devices. However, although ‘spin injectors’ capable of creating such currents have been developed, their efficiency has generally remained too low for practical applications. Now, Kimura, Hamaya and colleagues have significantly improved this efficiency by using a highly ordered cobalt-iron-silicon ‘Heusler’ Compound with high spin polarization. These findings highlight the potential of Heusler Compounds as spin injectors, and move the construction of functional spintronic devices one step forward. Heusler Compound spin injector with a high spin polarization dramatically improves the generation efficiency of the pure spin current compared with a conventional ferromagnetic metal.
Shinya Yamada - One of the best experts on this subject based on the ideXlab platform.
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magnetic properties and interfacial characteristics of all epitaxial Heusler Compound stacking structures
Physical Review B, 2016Co-Authors: Shinya Yamada, K Tanikawa, Syuta Honda, Junya Hirayama, Makoto Kawano, K Santo, Takeshi Kanashima, H ItohAbstract:We study magnetic properties and interfacial characteristics of all-epitaxial $D{0}_{3}\ensuremath{-}{\mathrm{Fe}}_{3}\mathrm{Si}/L{2}_{1}$- ${\mathrm{Fe}}_{3\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Si}/L{2}_{1}\ensuremath{-}{\mathrm{Co}}_{2}\mathrm{FeSi}$ Heusler-Compound trilayers grown on Ge(111) by room-temperature molecular beam epitaxy. We find that the magnetization reversal processes can be intentionally designed by changing the chemical composition of the intermediate ${\mathrm{Fe}}_{3\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Si}$ layers because of their tunable ferromagnetic-paramagnetic phase-transition temperature. From first-principles calculations, interfacial half metallicity in the ${\mathrm{Co}}_{2}\mathrm{FeSi}$ layer is nearly expected when the sequence of stacking layers along $\ensuremath{\langle}111\ensuremath{\rangle}$ of the ${\mathrm{Fe}}_{2}\mathrm{MnSi}/{\mathrm{Co}}_{2}\mathrm{FeSi}$ interface includes the atomic row of $L{2}_{1}$- or $B2$-ordered structures. We believe that ${\mathrm{Co}}_{2}\mathrm{FeSi}/{\mathrm{Fe}}_{2}\mathrm{MnSi}/{\mathrm{Co}}_{2}\mathrm{FeSi}$ trilayer systems stacked along $\ensuremath{\langle}111\ensuremath{\rangle}$ will open a new avenue for high-performance current-perpendicular-to-plane giant magnetoresistive devices with Heusler Compounds.
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effect of co fe substitution on room temperature spin polarization in co 3 x fe x si Heusler Compound films
Physical Review B, 2013Co-Authors: K Tanikawa, Masanobu Miyao, Shinya Yamada, Soichiro Oki, Ko Mibu, K HamayaAbstract:Using low-temperature molecular beam epitaxy, we study substitutions of Fe atoms for Co ones in Co_3-xFe_xSi Heusler-Compound films grown on Si and Ge. Even for the low-temperature grown Heusler-Compound films, the Co-Fe atomic substitution at A and C sites can be confirmed by the conversion electron M"ossbauer spectroscopy measurements. As a result, the magnetic moment and room-temperature spin polarization estimated by nonlocal spin-valve measurements are systematically changed with the Co-Fe substitutions. This study experimentally verified that the Co-Fe substitution in Co_3-xFe_xSi Heusler Compounds can directly affect the room-temperature spin polarization.
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Room-temperature generation of giant pure spin currents using epitaxial Co_2FeSi spin injectors
NPG Asia Materials, 2012Co-Authors: Takashi Kimura, Masanobu Miyao, Shinya Yamada, Naoki Hashimoto, Kohei HamayaAbstract:Spintronics: Current generationTakashi Kimura, Kohei Hamaya and co-workers have generated large pure spin currents at room temperature, with high efficiency. Spintronic devices, which use the spin of electrons as well as their charge, promise to be faster and less power-consuming than traditional charge-based electronic ones. A pure spin current — a flow that is not accompanied by charge current — seems to be a promising way to write information for such devices. However, although ‘spin injectors’ capable of creating such currents have been developed, their efficiency has generally remained too low for practical applications. Now, Kimura, Hamaya and colleagues have significantly improved this efficiency by using a highly ordered cobalt-iron-silicon ‘Heusler’ Compound with high spin polarization. These findings highlight the potential of Heusler Compounds as spin injectors, and move the construction of functional spintronic devices one step forward.Heusler Compound spin injector with a high spin polarization dramatically improves the generation efficiency of the pure spin current compared with a conventional ferromagnetic metal.AbstractThe generation, manipulation and detection of a pure spin current (i.e., the flow of spin angular momentum without a charge current) are prospective approaches for realizing next-generation spintronic devices with ultra-low electric power consumption. Conventional ferromagnetic electrodes such as Co and NiFe have been utilized as spin injectors to generate pure spin currents in nonmagnetic channels. However, the generation efficiency of pure spin currents is extremely low at room temperature, giving rise to a serious obstacle for device applications. Here we demonstrate the generation of giant pure spin currents at room temperature in lateral spin valve devices with a highly ordered Heusler-Compound Co_2FeSi (CFS) spin injector. The generation efficiency of pure spin currents from the CFS spin injectors is 10 times greater than that of the NiFe injectors, indicating that Heusler Compound spin injectors with high spin polarization enable us to materialize a high-performance lateral spin device. The present study is a technological jump in spintronics, and indicates the great potential of ferromagnetic Heusler Compounds with half metallicity for generating pure spin currents.
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Room-temperature generation of giant pure spin currents using epitaxial Co_2FeSi spin injectors
NPG Asia Materials, 2012Co-Authors: Takashi Kimura, Masanobu Miyao, Shinya Yamada, Naoki Hashimoto, Kohei HamayaAbstract:The generation, manipulation and detection of a pure spin current (i.e., the flow of spin angular momentum without a charge current) are prospective approaches for realizing next-generation spintronic devices with ultra-low electric power consumption. Conventional ferromagnetic electrodes such as Co and NiFe have been utilized as spin injectors to generate pure spin currents in nonmagnetic channels. However, the generation efficiency of pure spin currents is extremely low at room temperature, giving rise to a serious obstacle for device applications. Here we demonstrate the generation of giant pure spin currents at room temperature in lateral spin valve devices with a highly ordered Heusler-Compound Co_2FeSi (CFS) spin injector. The generation efficiency of pure spin currents from the CFS spin injectors is 10 times greater than that of the NiFe injectors, indicating that Heusler Compound spin injectors with high spin polarization enable us to materialize a high-performance lateral spin device. The present study is a technological jump in spintronics, and indicates the great potential of ferromagnetic Heusler Compounds with half metallicity for generating pure spin currents. Takashi Kimura, Kohei Hamaya and co-workers have generated large pure spin currents at room temperature, with high efficiency. Spintronic devices, which use the spin of electrons as well as their charge, promise to be faster and less power-consuming than traditional charge-based electronic ones. A pure spin current — a flow that is not accompanied by charge current — seems to be a promising way to write information for such devices. However, although ‘spin injectors’ capable of creating such currents have been developed, their efficiency has generally remained too low for practical applications. Now, Kimura, Hamaya and colleagues have significantly improved this efficiency by using a highly ordered cobalt-iron-silicon ‘Heusler’ Compound with high spin polarization. These findings highlight the potential of Heusler Compounds as spin injectors, and move the construction of functional spintronic devices one step forward. Heusler Compound spin injector with a high spin polarization dramatically improves the generation efficiency of the pure spin current compared with a conventional ferromagnetic metal.
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room temperature generation of giant pure spin currents using epitaxial co2fesi spin injectors
Npg Asia Materials, 2012Co-Authors: Takashi Kimura, Masanobu Miyao, Kohei Hamaya, Shinya Yamada, Naoki HashimotoAbstract:The generation, manipulation and detection of a pure spin current (i.e., the flow of spin angular momentum without a charge current) are prospective approaches for realizing next-generation spintronic devices with ultra-low electric power consumption. Conventional ferromagnetic electrodes such as Co and NiFe have been utilized as spin injectors to generate pure spin currents in nonmagnetic channels. However, the generation efficiency of pure spin currents is extremely low at room temperature, giving rise to a serious obstacle for device applications. Here we demonstrate the generation of giant pure spin currents at room temperature in lateral spin valve devices with a highly ordered Heusler-Compound Co2FeSi (CFS) spin injector. The generation efficiency of pure spin currents from the CFS spin injectors is 10 times greater than that of the NiFe injectors, indicating that Heusler Compound spin injectors with high spin polarization enable us to materialize a high-performance lateral spin device. The present study is a technological jump in spintronics, and indicates the great potential of ferromagnetic Heusler Compounds with half metallicity for generating pure spin currents. Takashi Kimura, Kohei Hamaya and co-workers have generated large pure spin currents at room temperature, with high efficiency. Spintronic devices, which use the spin of electrons as well as their charge, promise to be faster and less power-consuming than traditional charge-based electronic ones. A pure spin current — a flow that is not accompanied by charge current — seems to be a promising way to write information for such devices. However, although ‘spin injectors’ capable of creating such currents have been developed, their efficiency has generally remained too low for practical applications. Now, Kimura, Hamaya and colleagues have significantly improved this efficiency by using a highly ordered cobalt-iron-silicon ‘Heusler’ Compound with high spin polarization. These findings highlight the potential of Heusler Compounds as spin injectors, and move the construction of functional spintronic devices one step forward. Heusler Compound spin injector with a high spin polarization dramatically improves the generation efficiency of the pure spin current compared with a conventional ferromagnetic metal.
Gerhard H Fecher - One of the best experts on this subject based on the ideXlab platform.
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realization of spin gapless semiconductors the Heusler Compound mn2coal
Physical Review Letters, 2013Co-Authors: Siham Ouardi, Gerhard H Fecher, Claudia Felser, Jurgen KublerAbstract:: Recent studies have reported an interesting class of semiconductor materials that bridge the gap between semiconductors and half-metallic ferromagnets. These materials, called spin gapless semiconductors, exhibit a band gap in one of the spin channels and a zero band gap in the other and thus allow for tunable spin transport. Here, we report the first experimental verification of the spin gapless magnetic semiconductor Mn(2)CoAl, an inverse Heusler Compound with a Curie temperature of 720 K and a magnetic moment of 2 μ(B). Below 300 K, the Compound exhibits nearly temperature-independent conductivity, very low, temperature-independent carrier concentration, and a vanishing Seebeck coefficient. The anomalous Hall effect is comparatively low, which is explained by the symmetry properties of the Berry curvature. Mn(2) CoAl is not only suitable material for room temperature semiconductor spintronics, the robust spin polarization of the spin gapless semiconductors makes it very promising material for spintronics in general.
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increasing curie temperature in tetragonal mn2rhsn Heusler Compound through substitution of rh by co and mn by rh
Journal of Applied Physics, 2013Co-Authors: Vajiheh Alijani, Gerhard H Fecher, O Meshcheriakova, Juergen Winterlik, Guido Kreiner, Claudia FelserAbstract:The tetragonal Mn2RhSn Heusler Compound shows better lattice match with MgO than do Mn3−xGa and tetragonal Mn3−xCoxGa Heusler Compounds and hence is better suited for spin transfer torque applications. Beside the improved lattice match, this Compound shows a low saturation magnetic moment reduces the current to switch which makes it more relevant for application in spin transfer torque devices. This Compound shows a low Curie temperature; introducing Co into this system and increasing the Rh content leads to an increase in the Curie temperature. Doping with Co retains the tetragonal structure, with improved lattice match with MgO and low magnetic moment, intact up to x = 0.6, although doping with Rh changes the structure from tetragonal to cubic.
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Transport and optical properties of the gapless Heusler Compound PtYSb
Applied Physics Letters, 2011Co-Authors: Siham Ouardi, Jaroslav Hamrle, Gerhard H Fecher, Claudia Felser, Kamil Postava, Jaromir PistoraAbstract:This work presents a systematic study on the optical and transport properties of the Heusler Compound PtYSb. The optical properties were investigated in a wide spectral range from 10 meV to 6.5 eV and compared to ab-initio calculations. For photon energies below 2.5 eV, the optical absorption increases linearly with photon energy. This is related with the conical shape of the electronic structure in the vicinity of the Fermi energy. The optical spectra reveal a maximum band gap of about 60 meV. Furthermore, the temperature dependence of thermal conductivity, electrical resistivity, Seebeck coefficient and Hall mobility were investigated. PtYSb exhibits very good thermoelectric properties with a high figure of merit ZT of 0.2 and a Hall mobility μh of 300 cm2/Vs at 350 K, which is the highest value obtained for Heusler Compounds up to now. The carrier concentration ranges from 5 × 1018 at low temperature to 1019 cm−3 at 400 K.
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electronic and crystallographic structure hard x ray photoemission and mechanical and transport properties of the half metallic Heusler Compound co2mnge
Physical Review B, 2011Co-Authors: Siham Ouardi, Gerhard H Fecher, Claudia Felser, G Stryganyuk, Benjamin Balke, Andreea Beleanu, Xeniya Kozina, Werner Klos, Hartmut Schrader, Fabiano BernardiAbstract:This work reports on the electronic and crystalline structure and the mechanical, magnetic, and transport properties of the polycrystalline Heusler Compound Co2MnGe. The crystalline structure was examined in detail by extended x-ray absorption fine-structure spectroscopy and anomalous x-ray diffraction. The Compound exhibits a well-ordered L21 structure as is typical for Heusler Compounds with 2:1:1 stoichiometry. The low-temperature magnetic moment agrees well with the Slater-Pauling rule and indicates a half-metallic ferromagnetic state of the Compound, as is predicted by ab initio calculations. Transport measurements and hard x-ray photoelectron spectroscopy were performed to explain the electronic structure of the Compound. The obtained valence band spectra exhibit small energy shifts that are the result of the photoexcitation process, whereas electron-electron correlation in the ground state is negligible. The vibration and mechanical properties of the Compound were calculated. The observed hardness values are consistent to a covalent-like bonding of Co2MnGe.
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electronic structure and transport properties of the Heusler Compound co2tial
Journal of Physics D, 2009Co-Authors: Tanja Graf, Gerhard H Fecher, Joachim Barth, Jiirgen Winterlik, Claudia FelserAbstract:The properties of the Heusler Compound Co2TiAl were investigated in detail by experimental techniques and theoretical methods. X-ray diffraction measurements indicate that as-cast samples of the Compound exhibit the L21 structure with a small amount of B2-type disorder. This leads to a reduced saturation magnetization per formula unit of 0.747 μB. The Curie temperature is approximately 120 K. The transport properties are influenced by the change in the electronic structure at the Curie temperature, as revealed experimentally by conductivity, thermal transport and specific heat measurements. Different theoretical models based on ab initio calculations of the electronic structure are used to explain the experimental observations.
Masanobu Miyao - One of the best experts on this subject based on the ideXlab platform.
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effect of co fe substitution on room temperature spin polarization in co 3 x fe x si Heusler Compound films
Physical Review B, 2013Co-Authors: K Tanikawa, Masanobu Miyao, Shinya Yamada, Soichiro Oki, Ko Mibu, K HamayaAbstract:Using low-temperature molecular beam epitaxy, we study substitutions of Fe atoms for Co ones in Co_3-xFe_xSi Heusler-Compound films grown on Si and Ge. Even for the low-temperature grown Heusler-Compound films, the Co-Fe atomic substitution at A and C sites can be confirmed by the conversion electron M"ossbauer spectroscopy measurements. As a result, the magnetic moment and room-temperature spin polarization estimated by nonlocal spin-valve measurements are systematically changed with the Co-Fe substitutions. This study experimentally verified that the Co-Fe substitution in Co_3-xFe_xSi Heusler Compounds can directly affect the room-temperature spin polarization.
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Room-temperature generation of giant pure spin currents using epitaxial Co_2FeSi spin injectors
NPG Asia Materials, 2012Co-Authors: Takashi Kimura, Masanobu Miyao, Shinya Yamada, Naoki Hashimoto, Kohei HamayaAbstract:Spintronics: Current generationTakashi Kimura, Kohei Hamaya and co-workers have generated large pure spin currents at room temperature, with high efficiency. Spintronic devices, which use the spin of electrons as well as their charge, promise to be faster and less power-consuming than traditional charge-based electronic ones. A pure spin current — a flow that is not accompanied by charge current — seems to be a promising way to write information for such devices. However, although ‘spin injectors’ capable of creating such currents have been developed, their efficiency has generally remained too low for practical applications. Now, Kimura, Hamaya and colleagues have significantly improved this efficiency by using a highly ordered cobalt-iron-silicon ‘Heusler’ Compound with high spin polarization. These findings highlight the potential of Heusler Compounds as spin injectors, and move the construction of functional spintronic devices one step forward.Heusler Compound spin injector with a high spin polarization dramatically improves the generation efficiency of the pure spin current compared with a conventional ferromagnetic metal.AbstractThe generation, manipulation and detection of a pure spin current (i.e., the flow of spin angular momentum without a charge current) are prospective approaches for realizing next-generation spintronic devices with ultra-low electric power consumption. Conventional ferromagnetic electrodes such as Co and NiFe have been utilized as spin injectors to generate pure spin currents in nonmagnetic channels. However, the generation efficiency of pure spin currents is extremely low at room temperature, giving rise to a serious obstacle for device applications. Here we demonstrate the generation of giant pure spin currents at room temperature in lateral spin valve devices with a highly ordered Heusler-Compound Co_2FeSi (CFS) spin injector. The generation efficiency of pure spin currents from the CFS spin injectors is 10 times greater than that of the NiFe injectors, indicating that Heusler Compound spin injectors with high spin polarization enable us to materialize a high-performance lateral spin device. The present study is a technological jump in spintronics, and indicates the great potential of ferromagnetic Heusler Compounds with half metallicity for generating pure spin currents.
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Room-temperature generation of giant pure spin currents using epitaxial Co_2FeSi spin injectors
NPG Asia Materials, 2012Co-Authors: Takashi Kimura, Masanobu Miyao, Shinya Yamada, Naoki Hashimoto, Kohei HamayaAbstract:The generation, manipulation and detection of a pure spin current (i.e., the flow of spin angular momentum without a charge current) are prospective approaches for realizing next-generation spintronic devices with ultra-low electric power consumption. Conventional ferromagnetic electrodes such as Co and NiFe have been utilized as spin injectors to generate pure spin currents in nonmagnetic channels. However, the generation efficiency of pure spin currents is extremely low at room temperature, giving rise to a serious obstacle for device applications. Here we demonstrate the generation of giant pure spin currents at room temperature in lateral spin valve devices with a highly ordered Heusler-Compound Co_2FeSi (CFS) spin injector. The generation efficiency of pure spin currents from the CFS spin injectors is 10 times greater than that of the NiFe injectors, indicating that Heusler Compound spin injectors with high spin polarization enable us to materialize a high-performance lateral spin device. The present study is a technological jump in spintronics, and indicates the great potential of ferromagnetic Heusler Compounds with half metallicity for generating pure spin currents. Takashi Kimura, Kohei Hamaya and co-workers have generated large pure spin currents at room temperature, with high efficiency. Spintronic devices, which use the spin of electrons as well as their charge, promise to be faster and less power-consuming than traditional charge-based electronic ones. A pure spin current — a flow that is not accompanied by charge current — seems to be a promising way to write information for such devices. However, although ‘spin injectors’ capable of creating such currents have been developed, their efficiency has generally remained too low for practical applications. Now, Kimura, Hamaya and colleagues have significantly improved this efficiency by using a highly ordered cobalt-iron-silicon ‘Heusler’ Compound with high spin polarization. These findings highlight the potential of Heusler Compounds as spin injectors, and move the construction of functional spintronic devices one step forward. Heusler Compound spin injector with a high spin polarization dramatically improves the generation efficiency of the pure spin current compared with a conventional ferromagnetic metal.
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room temperature generation of giant pure spin currents using epitaxial co2fesi spin injectors
Npg Asia Materials, 2012Co-Authors: Takashi Kimura, Masanobu Miyao, Kohei Hamaya, Shinya Yamada, Naoki HashimotoAbstract:The generation, manipulation and detection of a pure spin current (i.e., the flow of spin angular momentum without a charge current) are prospective approaches for realizing next-generation spintronic devices with ultra-low electric power consumption. Conventional ferromagnetic electrodes such as Co and NiFe have been utilized as spin injectors to generate pure spin currents in nonmagnetic channels. However, the generation efficiency of pure spin currents is extremely low at room temperature, giving rise to a serious obstacle for device applications. Here we demonstrate the generation of giant pure spin currents at room temperature in lateral spin valve devices with a highly ordered Heusler-Compound Co2FeSi (CFS) spin injector. The generation efficiency of pure spin currents from the CFS spin injectors is 10 times greater than that of the NiFe injectors, indicating that Heusler Compound spin injectors with high spin polarization enable us to materialize a high-performance lateral spin device. The present study is a technological jump in spintronics, and indicates the great potential of ferromagnetic Heusler Compounds with half metallicity for generating pure spin currents. Takashi Kimura, Kohei Hamaya and co-workers have generated large pure spin currents at room temperature, with high efficiency. Spintronic devices, which use the spin of electrons as well as their charge, promise to be faster and less power-consuming than traditional charge-based electronic ones. A pure spin current — a flow that is not accompanied by charge current — seems to be a promising way to write information for such devices. However, although ‘spin injectors’ capable of creating such currents have been developed, their efficiency has generally remained too low for practical applications. Now, Kimura, Hamaya and colleagues have significantly improved this efficiency by using a highly ordered cobalt-iron-silicon ‘Heusler’ Compound with high spin polarization. These findings highlight the potential of Heusler Compounds as spin injectors, and move the construction of functional spintronic devices one step forward. Heusler Compound spin injector with a high spin polarization dramatically improves the generation efficiency of the pure spin current compared with a conventional ferromagnetic metal.