<i>Ab initio</i>studies of the tunneling magneto-Seebeck effect: Influence of magnetic material

Heiliger, Christian; Czerner, Michael

doi:10.1103/physrevb.87.224412

Cited by 30 publications

(50 citation statements)

References 29 publications

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“…However, there are a few variations between the different experiments: First, the sign of the Seebeck voltage remains unclear, which could also vary depending on temperature and Co-Fecomposition. 24 Further, it was reported by Ref. 11 that no magnetic effect is observed in the thermocurrent obtained with alumina-barriers and that Seebeck voltages could be observed when heating the electrical leads a distance of the order of millimeters away from the MTJ.…”

Section: 10mentioning

confidence: 89%

Time-resolved measurement of the tunnel magneto-Seebeck effect in a single magnetic tunnel junction

Boehnke

Walter

Roschewsky

et al. 2013

Review of Scientific Instruments

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Recently, several groups have reported spin-dependent thermoelectric effects in magnetic tunnel junctions. In this paper, we present a setup for time-resolved measurements of thermovoltages and thermocurrents of a single micro-to nanometer-scaled tunnel junction. An electrically modulated diode laser is used to create a temperature gradient across the tunnel junction layer stack. This laser modulation technique enables the recording of time-dependent thermovoltage signals with a temporal resolution only limited by the preamplifier for the thermovoltage. So far, time-dependent thermovoltage could not be interpreted. Now, with the setup presented in this paper, it is possible to distinguish different Seebeck voltage contributions to the overall measured voltage signal in the µs time regime. A model circuit is developed that explains those voltage contributions on different sample types. Further, it will be shown that a voltage signal arising from the magnetic tunnel junction can only be observed when the laser spot is directly centered on top of the magnetic tunnel junction, which allows a lateral separation of the effects.

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Section: 10mentioning

confidence: 89%

Time-resolved measurement of the tunnel magneto-Seebeck effect in a single magnetic tunnel junction

Boehnke

Walter

Roschewsky

et al. 2013

Review of Scientific Instruments

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“…In particular, a giant magnetothermopower effect has been predicted by magnon-assisted thermal transport [20]. Ab initio calculations have been performed for MgObased MTJs, where the TMT dependence on temperature was computed [21,26,27], and which has been used to understand previously mentioned experiments [14]. Similar calculations have been performed for GaAs-based MTJs [28].…”

Section: Introductionmentioning

confidence: 99%

Tunneling magnetothermopower in magnetic tunnel junctions

2014

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Thermally induced spin-dependent transport across magnetic tunnel junctions (MTJs) is theoretically investigated. We analyze the thermal analog of Slonczewski's model (as well as its limiting case-Julliere's model) of tunneling magnetoresistance and obtain analytical expressions for the junction thermopower and the tunneling magnetothermopower (TMT). The analytical model is tested numerically for the special case of an Al 2 O 3 -based MTJ, for which we analyze the dependence of the thermopower and TMT on the relative magnetization orientations, as well as on the barrier height and thickness. We show that at a certain barrier height TMT vanishes, separating the region of positive and negative TMT. As its electrical prototype, this thermal spin transport model should serve as a phenomenological benchmark for analyzing experimental and first-principles calculations of thermopower in magnetic tunnel junctions. The analytical expressions can be used as a first estimate of the magnetothermopower of the junctions using ab initio band structure data of the junction ferromagnets.

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“…The CPA-NVC provides a non-equilibrium effective medium description of the disordered nanoelectronics, and has achieved considerable success in the simulation of disordered nanoelectronics. [30][31][32][33][34][35][36][37][38][39][40] In this method, the NVC accounts for both effects of the multiple impurity scattering and the non-equilibrium quantum statistics, which it is named after. Besides, theoretical efforts have also been spent to avoid the NVC by calculating G < directly through an approach called non-equilibrium CPA (NECPA).…”

Section: Introductionmentioning

confidence: 99%

Generalized nonequilibrium vertex correction method in coherent medium theory for quantum transport simulation of disordered nanoelectronics

Yan

2016

Phys. Rev. B

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In realistic nanoelectronics, disordered impurities/defects are inevitable and play important roles in electron transport. However, due to the lack of effective quantum transport method to do disorder average, the important effects of disorders remain largely un-explored or poorly understood. Here, we report a generalized non-equilibrium vertex correction method with coherent potential approximation for the non-equilibrium quantum transport simulation of disordered nanoelectronics. In this method, the disorder average of various Green's functions are computed by a generalized coherent potential approximation. A generalized non-equilibrium vertex correction algorithm is then developed to calculate disorder average of the product of any two real time single-particle Green's functions. We obtain nine non-equilibrium vertex corrections and find they can be solved by a set of simple linear equations. As a result, the averaged non-equilibrium density matrix and various important transport properties, including averaged current, disordered induced current fluctuation and the averaged shot noise, can all be efficiently computed in a unified simple scheme. Moreover, the relationship between the non-equilibrium vertex correction method and the nonequilibrium coherent potential approximation theory is clarified, and we prove the non-equilibrium coherent potential equals the non-equilibrium vertex correction and this equivalence is guaranteed by the Keldysh's formulas. In addition, a generalized form of conditionally averaged non-equilibrium Green's function is derived to incorporate with density functional theory to enable first-principles quantum transport simulation. Our approach provides a unified, efficient and self-consistent method for simulating non-equilibrium quantum transport through disordered nanoelectronics.

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Ab initiostudies of the tunneling magneto-Seebeck effect: Influence of magnetic material

Cited by 30 publications

References 29 publications

Time-resolved measurement of the tunnel magneto-Seebeck effect in a single magnetic tunnel junction

Time-resolved measurement of the tunnel magneto-Seebeck effect in a single magnetic tunnel junction

Tunneling magnetothermopower in magnetic tunnel junctions

Generalized nonequilibrium vertex correction method in coherent medium theory for quantum transport simulation of disordered nanoelectronics

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