Thermoelectricity and disorder of FeCo/MgO/FeCo magnetic tunnel junctions

Wang, Shi Zhuo; Xia, Ke; Bauer, G.

doi:10.1103/physrevb.90.224406

Cited by 20 publications

(15 citation statements)

References 31 publications

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“…In device A where we observed a TMR of 87.5% (with parallel resistance R P =1.6 kΩ and antiparallel resistance R AP =3.0 kΩ) when I = 150 µA, we obtain the corresponding conductivities σ P =0.093 S/m and σ AP =0.05 S/m, respectively. Although the thermal conductance of MgO is expected to depend on the magnetic configuration of the MTJ [13], for simplicity, we do not take this scenario into account. In the estimation of the magneto-Peltier coefficient, we match the measured Peltier signals by varying the magneto-Seebeck coefficient ∆S = ∆S AP − ∆S P .…”

Section: Finite Element Thermoelectric Modelmentioning

confidence: 99%

Comparison of the magneto-Peltier and magneto-Seebeck effects in magnetic tunnel junctions

et al. 2015

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Understanding heat generation and transport processes in a magnetic tunnel junction (MTJ) is a significant step towards improving its application in current memory devices. Recent work has experimentally demonstrated the magneto-Seebeck effect in MTJs, where the Seebeck coefficient of the junction varies as the magnetic configuration changes from a parallel (P) to an anti-parallel (AP) configuration. Here we report the study on its as-yet-unexplored reciprocal effect, the magnetoPeltier effect, where the heat flow carried by the tunneling electrons is altered by changing the magnetic configuration of the MTJ. The magneto-Peltier signal that reflects the change in the temperature difference across the junction between the P and AP configurations scales linearly with the applied current in the small bias but is greatly enhanced in the large bias regime, due to higher-order Joule heating mechanisms. By carefully extracting the linear response which reflects the magneto-Peltier effect, and comparing it with the magneto-Seebeck measurements performed on the same device, we observe results consistent with Onsager reciprocity. We estimate a magnetoPeltier coefficient of 13.4 mV in the linear regime using a three-dimensional thermoelectric model. Our result opens up the possibility of programmable thermoelectric devices based on the Peltier effect in MTJs.The electrical resistance of a magnetic tunnel junction (MTJ), a stack of two ferromagnetic layers separated by an insulating tunnel barrier, depends on the relative magnetic orientation of the two magnetic layers [1][2][3]. This tunnel magnetoresistance (TMR) effect puts MTJs at the forefront of the applications in the field of spintronics [4]. Spin caloritronics [5][6][7] is an emerging field that couples thermoelectric effects with spintronics. Many interesting physical phenomena were discovered such as the spin (-dependent) Seebeck effect in magnetic metal [8], magnetic semiconductor [9] and magnetic insulator [10]. Particularly, in spin tunneling devices, the magneto-Seebeck effect was theoretically studied [11][12][13][14] and experimentally observed [15][16][17][18][19] in MTJs, where the Seebeck coefficient of the junction can be varied by changing the magnetic configuration. More recently, the spin (-dependent) Peltier effect that is driven by spin (polarized) currents has been experimentally observed in metallic [20,21] and insulating ferromagnets [22], which are shown to obey the Thomson-Onsager reciprocity relation [23][24][25] to the spin (-dependent) Seebeck effect. From this relation, the reciprocal effect of the magneto-Seebeck effect, which can be named as magneto-Peltier effect, is also expected in MTJs (see Fig. 1(a)(b)).However, experimental studies of the magneto-Peltier effect have not been reported so far. Its small effect compared to the often-dominant Joule heating effects has left the experimental observation elusive. In this work, we report the first experimental study of the magneto-Peltier effect as well as higher order heating effects, and...

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Section: Finite Element Thermoelectric Modelmentioning

confidence: 99%

Comparison of the magneto-Peltier and magneto-Seebeck effects in magnetic tunnel junctions

et al. 2015

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“…While these investigations have focused only on the bulk electronic structure of the ferromagnetic electrode, the interface property is also an important factor for the Seebeck effect in MTJs. For example, the interfacial termination has been found to affect the Seebeck effect in MTJs [18,23,24]. Furthermore, Jia et al [25] have reported that the interface resonant tunneling significantly changes the energy dependence of the tunneling conductance.…”

Section: Introductionmentioning

confidence: 99%

Strain-induced enhancement of the Seebeck effect in magnetic tunneling junctions via interface resonant tunneling: Ab initio study

et al. 2020

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We investigate the thermoelectric properties of Fe/MgO/Fe(001) magnetic tunnel junctions (MTJs) by means of the linear-response theory combined with a first-principles-based Landauer-Büttiker approach. We find that the Seebeck coefficient of Fe/MgO/Fe(001) MTJs strongly depends on the barrier thickness and the tetragonal distortion. A compressive tetragonal distortion of the in-plane lattice parameter in the MTJs provides interface resonant states just above the Fermi energy. This causes resonant tunneling in the MTJs and significantly enhances the Seebeck coefficient when the thickness of the MgO barrier is around 1 nm (four or five atomic layers of MgO). Moreover, an extensive tetragonal distortion of the in-plane lattice parameter pushes the interface states away from the Fermi energy, leading to a reduction of the Seebeck coefficient. Furthermore, we find that the interface resonant tunneling enhances the power factor of the MTJs for the compressive distortion. These results indicate that control of the barrier thickness and the tetragonal distortion will be effective for maximizing the thermoelectric properties of MTJs.

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“…[2][3][4]) as well as ab-initio formalism (e.g. [5,6]). The Seebeck effect in such systems depends significantly on the magnetic configuration of the junctions [1][2][3][4][5][6], so potentially it can be used in constructing various spintronic devices.…”

Section: Introductionmentioning

confidence: 99%

“…[5,6]). The Seebeck effect in such systems depends significantly on the magnetic configuration of the junctions [1][2][3][4][5][6], so potentially it can be used in constructing various spintronic devices. It is known that many effects connected with electron transport in single tunnel junctions can be slightly enhanced in double tunnel junctions due to the resonant tunnelling through such systems by resonant states.…”

Section: Introductionmentioning

confidence: 99%

The Seebeck Effect in Double Tunnel Junctions with Ferromagnetic Electrodes and Central Layer Separated by Nonmagnetic Barriers

Wilczyński

2018

Acta Phys. Pol. A

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The Seebeck effect is analysed in the double planar tunnel junctions consisting of ferromagnetic electrodes and the central layer separated by nonmagnetic barriers with the arbitrary angle between magnetic moments in neighbouring ferromagnetic layers. The Seebeck coefficient is calculated as a function of the thickness of the central layer. The influence of temperature of the junction and the relative orientation of magnetic moments in ferromagnetic layers on this coefficient is also analysed. Calculations are performed in the linear response theory using the free-electron model. It has been found that the Seebeck coefficient oscillates with the thickness of the central layer and can be strongly enhanced in the junction with special central layer thickness due to electron tunnelling by resonant states. The form of the observed oscillations depends on the temperature of the junction. The magnitude of the Seebeck coefficient usually increases with the increase of the angle between magnetic moments in the neighbouring ferromagnetic layers as in the case of single junctions. However, in the junctions with the specially designated central layer the decrease of the magnitude of the Seebeck coefficient with the increase of this angle can be observed.

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Thermoelectricity and disorder of FeCo/MgO/FeCo magnetic tunnel junctions

Cited by 20 publications

References 31 publications

Comparison of the magneto-Peltier and magneto-Seebeck effects in magnetic tunnel junctions

Comparison of the magneto-Peltier and magneto-Seebeck effects in magnetic tunnel junctions

Strain-induced enhancement of the Seebeck effect in magnetic tunneling junctions via interface resonant tunneling: Ab initio study

The Seebeck Effect in Double Tunnel Junctions with Ferromagnetic Electrodes and Central Layer Separated by Nonmagnetic Barriers

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