Large magneto-Seebeck effect in magnetic tunnel junctions with half-metallic Heusler electrodes

Boehnke, Alexander; Martens, Ulrike; Sterwerf, Christian; Niesen, Alessia; Huebner, Torsten; Ehe, Marvin von der; Meinert, Markus; Kuschel, Timo; Thomas, Andy; Heiliger, Christian; Münzenberg, Markus; Reiss, Günter

doi:10.1038/s41467-017-01784-x

Cited by 50 publications

(43 citation statements)

References 51 publications

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“…The microscopic origin together with theoretical predictions of the TMS for multiple CoFe compositions with MgO barriers is given in reference [5,6] and is calculated by: TMS = ap − p min (| ap |, | p |) . (1) The TMS effect has been observed and analyzed for various combinations of barrier and electrode materials, showing thermovoltages in the μV range for MgO [7][8][9][10][11][12][13] andMgAl 2 O 4 [14,15], and reaching themV range for Heusler based MTJs [16]. All examined material configurations result in specific TMS ratios.…”

Section: Introductionmentioning

confidence: 99%

Anomalous Nernst effect and three-dimensional temperature gradients in magnetic tunnel junctions

et al. 2018

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Localized laser heating creates temperature gradients in all directions and thus leads to three-dimensional electron flux in metallic materials. Temperature gradients in combination with material magnetization generate thermomagnetic voltages. The interplay between these direction-dependent temperature gradients and the magnetization along with their control enable to manipulate the generated voltages, e.g. in magnetic nanodevices. We identify the anomalous Nernst effect (ANE) generated on a nanometer length scale by micrometer sized temperature gradients in magnetic tunnel junctions (MTJs). In a systematic study, we extract the ANE by analyzing the influence of in-plane temperature gradients on the tunnel magneto-Seebeck effect (TMS) in three dimensional devices. To investigate these effects, we utilize in-plane magnetized MTJs based on CoFeB electrodes with an MgO tunnel barrier. Due to our measurement configuration, there is no necessity to disentangle the ANE from the spin Seebeck effect in inverse spin-Hall measurements. The temperature gradients are created by a tightly focused laser spot. The spatial extent of the measured effects is defined by the MTJ size, while the spatial resolution is given by the laser spot size and the step size of its lateral translation. This method is highly sensitive to low voltages and yields an ANE coefficient of ≈ . ⋅ − for CoFeB. In general, TMS investigations in MTJs are motivated by the usage of otherwise wasted heat in magnetic memory devices for read/write operations. Here, the additionally generated ANE effect allows to expand the MTJs' functionality from simple memory storage to nonvolatile logic devices and opens new application fields such as direction dependent temperature sensing with the potential for further downscaling.

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Section: Introductionmentioning

confidence: 99%

Anomalous Nernst effect and three-dimensional temperature gradients in magnetic tunnel junctions

et al. 2018

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“…Last but not least, Heusler compounds offer a notably promising route towards magnetic Weyl semimetals [7]. Weyl semimetals can potentially host unique transport phenomena because of the nontrivial topology of the band structure [8][9][10], which also makes the spin-caloritronic response of Weyl semimentals very interesting [11][12][13][14]. One of the key effects in spin-caloritronic research is the anomalous Nernst effect (ANE), which is the thermal counterpart of the anomalous Hall effect (AHE).…”

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confidence: 99%

Large anomalous Nernst effect in thin films of the Weyl semimetal Co2MnGa

Reichlová

Schlitz

Beckert

et al. 2018

Applied Physics Letters

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109

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The magneto-thermoelectric properties of Heusler compound thin films are very diverse. Here, we discuss the anomalous Nernst response of Co 2 MnGa thin films. We systematically study the anomalous Nernst coefficient as a function of temperature, and we show that unlike the anomalous Hall effect, the anomalous Nernst effect in Co 2 MnGa strongly varies with temperature. We exploit the on-chip thermometry technique to quantify the thermal gradient, which enables us to directly evaluate the anomalous Nernst coefficient. We compare these results to a reference CoFeB thin film. We show that the 50-nm-thick Co 2 MnGa films exhibit a large anomalous Nernst effect of -2 µV/K at 300 K, whereas the 10-nm-thick Co 2 MnGa film exhibits a significantly smaller anomalous Nernst coefficient despite having similar volume magnetizations. These findings suggest that the microscopic origin of the anomalous Nernst effect in Co 2 MnGa is complex and may contain contributions from skew-scattering, side-jump or intrinsic Berry phase. In any case, the large anomalous Nernst coefficent of Co 2 MnGa thin films at room temperature makes this material system a very promising candidate for efficient spin-caloritronic devices.

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“…The experimental equipment and theoretical implementations are already on a very high level, so that ab initio calculations of band structure and transmission function nicely agree with the features that are observed in experiments. This scientific tango between theory and experiment [106] led, for example, to the prediction and experimental confirmation of high TMS ratios in MTJs with half-metallic Heusler electrodes [16]. We further presented the increase of thermovoltages for the use of MgAl 2 O 4 (MAO) barriers with an optimized barrier thickness of 2.6 nm [67].…”

Section: Discussionmentioning

confidence: 94%

Tunnel magneto-Seebeck effect

Kuschel¹,

Czerner²,

Walowski³

et al. 2019

J. Phys. D: Appl. Phys.

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The interplay of charge, spin and heat transport is investigated in the fascinating research field of spin caloritronics, the marriage of spintronics and thermoelectrics. Here, many new spin-dependent thermal transport phenomena in magnetic nanostructures have been explored in the recent years. One of them is the tunnel magneto-Seebeck (TMS) effect in magnetic tunnel junctions (MTJs) that has large potential for future nanoelectronic devices, such as nanostructured sensors for threedimentional thermal gradients, or scanning tunneling microscopes driven by temperature differences. The TMS describes the dependence of the MTJ's thermopower on its magnetic configuration when a thermal gradient is applied. In this review, we highlight the successful way from first observation of the TMS in 2011 to current ongoing developments in this research area. We emphasize on different heating techniques, material designs, applications, and additional physical aspects such as the role of the thermal conductivity of the barrier material. We further demonstrate the efficient interplay between ab initio calculations and experiments within this field, as this has led, e.g., to the detection of large TMS ratios in MTJs with half-metallic Heusler electrodes.

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Large magneto-Seebeck effect in magnetic tunnel junctions with half-metallic Heusler electrodes

Cited by 50 publications

References 51 publications

Anomalous Nernst effect and three-dimensional temperature gradients in magnetic tunnel junctions

Anomalous Nernst effect and three-dimensional temperature gradients in magnetic tunnel junctions

Large anomalous Nernst effect in thin films of the Weyl semimetal Co2MnGa

Tunnel magneto-Seebeck effect

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