Dependence of transverse magnetothermoelectric effects on inhomogeneous magnetic fields

Shestakov, Anatoly S.; Schmid, Maximilian; Meier, Daniel; Kuschel, Timo; Back, Christian

doi:10.1103/physrevb.92.224425

Cited by 14 publications

(12 citation statements)

References 24 publications

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“…Given large uncertainties of the experimental results for the YIG-Pt bilayer 6 , especially regarding the values of the LSSE coefficients, a quantitative description of the characteristics of a LSSE device is still lacking. In the literature one may find different experimental setups using different ways of determining and generating ∇ T such as Joule heating in an external heater 4 19 , laser heating 20 , Peltier heating 10 13 21 , current-induced heating in the sample 22 , heating with electric contact needles 14 17 , on-chip heater devices 23 24 and rotatable thermal gradients 25 . However, it is clear that the LSSE coefficient must not depend on the choice of set-up or measurement method but only on the material and device geometry.…”

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confidence: 99%

Longitudinal spin Seebeck coefficient: heat flux vs. temperature difference method

Sola

Bougiatioti

Kuepferling

et al. 2017

Sci Rep

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The determination of the longitudinal spin Seebeck effect (LSSE) coefficient is currently plagued by a large uncertainty due to the poor reproducibility of the experimental conditions used in its measurement. In this work we present a detailed analysis of two different methods used for the determination of the LSSE coefficient. We have performed LSSE experiments in different laboratories, by using different setups and employing both the temperature difference method and the heat flux method. We found that the lack of reproducibility can be mainly attributed to the thermal contact resistance between the sample and the thermal baths which generate the temperature gradient. Due to the variation of the thermal resistance, we found that the scaling of the LSSE voltage to the heat flux through the sample rather than to the temperature difference across the sample greatly reduces the uncertainty. The characteristics of a single YIG/Pt LSSE device obtained with two different setups was (1.143 ± 0.007) 10−7 Vm/W and (1.101 ± 0.015) 10−7 Vm/W with the heat flux method and (2.313 ± 0.017) 10−7 V/K and (4.956 ± 0.005) 10−7 V/K with the temperature difference method. This shows that systematic errors can be considerably reduced with the heat flux method.

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confidence: 99%

Longitudinal spin Seebeck coefficient: heat flux vs. temperature difference method

Sola

Bougiatioti

Kuepferling

et al. 2017

Sci Rep

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“…The first occurs in samples with magnetic anisotropy19, while the latter can be attributed to unintended out-of-plane temperature gradients20 due to heat flux into the surrounding region21 or through the electric contacts22. Recently, the influence of inhomogeneous magnetic fields was added to the list of uncertainties for TSSE experiments23. Despite first reports, the TSSE could not be reproduced neither for metals192021222324, for semiconductors25 nor insulators26.…”

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confidence: 99%

“…Recently, the influence of inhomogeneous magnetic fields was added to the list of uncertainties for TSSE experiments23. Despite first reports, the TSSE could not be reproduced neither for metals192021222324, for semiconductors25 nor insulators26.…”

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confidence: 99%

“…Different techniques to apply thermal gradients include Joule heating in an external heater914, laser heating833, Peltier heating52123, current-induced heating in the sample34, heating with electric contact needles2226 and on-chip heater devices35. In this work we present a setup, which uses Peltier heating as a method for heating and cooling purposes to cover a larger working temperature range.…”

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confidence: 99%

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Quantitative separation of the anisotropic magnetothermopower and planar Nernst effect by the rotation of an in-plane thermal gradient

Reimer

Meier

Bovender

et al. 2017

Sci Rep

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A thermal gradient as the driving force for spin currents plays a key role in spin caloritronics. In this field the spin Seebeck effect (SSE) is of major interest and was investigated in terms of in-plane thermal gradients inducing perpendicular spin currents (transverse SSE) and out-of-plane thermal gradients generating parallel spin currents (longitudinal SSE). Up to now all spincaloric experiments employ a spatially fixed thermal gradient. Thus, anisotropic measurements with respect to well defined crystallographic directions were not possible. Here we introduce a new experiment that allows not only the in-plane rotation of the external magnetic field, but also the rotation of an in-plane thermal gradient controlled by optical temperature detection. As a consequence, the anisotropic magnetothermopower and the planar Nernst effect in a permalloy thin film can be measured simultaneously. Thus, the angular dependence of the magnetothermopower with respect to the magnetization direction reveals a phase shift, that allows the quantitative separation of the thermopower, the anisotropic magnetothermopower and the planar Nernst effect.Adding the spin degree of freedom to conventional charge-based electronics opens the field of spintronics 1,2 with promising advantages such as decreased electric power consumption and increased integration densities. While spinelectronics use only voltages as driving force for currents, thermal gradients and the interaction between spins and heat currents have already been shown to provide new effects. Spin caloritronics investigate these interactions and promotes the search for applications such as heat sensors or waste heat recyclers 3,4 , that can improve thermoelectric devices.One of the most important and well established phenomena in spin caloritronics is the longitudinal spin Seebeck effect (LSSE) [5][6][7][8][9][10][11] , which uses typically out-of-plane thermal gradients in magnetic thin films for the generation of a spin current parallel to the thermal gradient. This pure spin current is then injected into an adjacent non-magnetic conductor with high spin-orbit coupling, e.g. Pt, which transforms the spin current into an electric voltage via the inverse spin Hall effect (ISHE). In very recent investigations, the LSSE was even detected without any Pt and ISHE by the use of the anomalous Hall effect in Au 12 and by time-resolved magnetooptic Kerr effect in Au and Cu 13 . Besides the application of an out-of-plane thermal gradient, effects driven by in-plane thermal gradients were also investigated. The transverse spin Seebeck effect (TSSE), the spin current generation perpendicular to an in-plane thermal gradient, was reported for metals 14 , semiconductors 15 and insulators 16 . However, it has been noted that TSSE experiments in metals and semiconductors can be influenced by parasitic effects like the planar

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“…[ 49,50 ] As yet, there is still no direct evidence to show that the TNE is truly induced either by skyrmions [ 51 ] or other topological spin structures. [ 52,53 ] Moreover, the observed signal could be a parasitic effect in the measured ANE due to inhomogeneities in the magnetic field [ 54 ] and heat flow, [ 55 ] or other thermal related effects, such as the planar Nernst effect (PNE) [ 31,56,57 ] and the anisotropic magnetothermoelectric power (AMTEP), [ 26,54 ] which can be generated when temperature gradient and magnetic field are both in the sample plane. Angle‐dependent investigations of the AMTEP and PNE have been performed to verify the relation between these two effects.…”

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confidence: 99%

Spin‐Dependent Thermoelectric Transport in Cobalt‐Based Heusler Alloys

Granville

2020

Annalen der Physik

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Sitting at the intersection of spintronics and thermoelectricity, research investigating the coupling of thermoelectric, magnetic, and electrical transport properties in materials has recently found that the ferromagnetic Heusler alloys are the ideal testbeds. These materials have attracted a lot of attention due to their useful magnetotransport properties and the possibility of tailoring these properties by modifying their composition or producing heterostructures. With the diverse range of interesting phenomena in the Heusler alloys, ferromagnetic Heusler alloys are also ideal candidates for engineering spin caloritronic devices that can take advantage of the interplay of the physics of heat flow, magnetism, and electric potential. The fundamental physical concepts important to spin-dependent thermoelectrics research are introduced and recent studies of several ferromagnetic Heusler compounds are reviewed, highlighting some exceptional latest experiments on half-metallic Co 2 TiSn and the ferromagnetic Weyl semimetal Co 2 MnGa. Furthermore, the potential to generate useful magnetothermoelectric voltages in electronic devices based on the anomalous Nernst effect is discussed.

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Dependence of transverse magnetothermoelectric effects on inhomogeneous magnetic fields

Cited by 14 publications

References 24 publications

Longitudinal spin Seebeck coefficient: heat flux vs. temperature difference method

Longitudinal spin Seebeck coefficient: heat flux vs. temperature difference method

Quantitative separation of the anisotropic magnetothermopower and planar Nernst effect by the rotation of an in-plane thermal gradient

Spin‐Dependent Thermoelectric Transport in Cobalt‐Based Heusler Alloys

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