Influence of the thermal interface resistance on the thermovoltage of a magnetic tunnel junction

Böhnert, Tim; Dutra, R.; Sommer, R.L.; Paz, Elvira; Serrano-Guisan, S.; Ferreira, Ricardo; Freitas, P. P.

doi:10.1103/physrevb.95.104441

Cited by 29 publications

(24 citation statements)

References 19 publications

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“…Most of Joule energy is released after the electrons tunneling in the receiving magnetic electrode adjacent to the MgO barrier. Therefore, considering that the thermal conductivity of thin MgO barrier is much lower than that of bulk MgO [21], the storage layer reaches up to 10% higher temperature if the current polarity is such that the storage layer receives the tunneling electrons. This effect becomes more significant in the case of MgO-based capping layer since the storage layer appears to be thermally insulated between two MgO layers with low thermal conductivity.…”

Section: Methodsmentioning

confidence: 99%

“…Bandiera et al proposed a concept of thermally assisted STT-MRAM in which the heating due to the STT write current is also used to induce an anisotropy reorientation from out-ofplane to in-plane [20]. Moreover, recent experiments have shown that the MgO/CoFeB interface with thin MgO tunnel barrier have a much lower (more than two orders of magnitude) thermal conductivity than what could be expected from the bulk value [21]. In double barrier MTJs in which the storage layer is sandwiched between two MgO barriers, this further enhances the Joule heating of the storage layer.…”

Section: Introductionmentioning

confidence: 99%

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Impact of Joule heating on the stability phase diagrams of perpendicular magnetic tunnel junctions

et al. 2018

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Measured switching voltage-field (V-H) diagrams of perpendicular magnetic tunnel junctions (pMTJ) exhibit unexpected behavior at high voltages associated with significant heating of the storage layer. The boundaries deviate from the critical lines corresponding to the coercive field, which contrasts with the theoretically predicted behavior of a standard macrospin-based model. Combining recent experimental studies of the temperature dependence of spin polarization and perpendicular magnetic anisotropy (PMA) we are proposing a modified model. Our approach takes into account the Joule heating during the writing pulse, which reduces the spin polarization and the anisotropy, thereby reducing the spin torque efficiency and the coercive field during the switching. The numerical macrospin simulations based on this model are in agreement with our experimental measurements and consistent with the results derived from the linearization of Landau-Lifshitz-Gilbert equation.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Impact of Joule heating on the stability phase diagrams of perpendicular magnetic tunnel junctions

et al. 2018

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“…Hence, there is an ongoing discussion about the actual thermal conductivity of thin insulating films [25][26][27] . With the simulated temperature differences, the Seebeck coefficients for the MAO and the MgO MTJ with the highest TMS ratios are calculated (via TMS =…”

Section: Thermovoltages and Seebeck Coefficientsmentioning

confidence: 99%

Enhancement of thermovoltage and tunnel magneto-Seebeck effect in CoFeB-based magnetic tunnel junctions by variation of the MgAl2O4 and MgO barrier thickness

Huebner

Martens²,

Walowski³

et al. 2017

Phys. Rev. B

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We investigate the influence of the barrier thickness of Co40Fe40B20 based magnetic tunnel junctions on the laser-induced tunnel magneto-Seebeck effect. Varying the barrier thickness from 1 nm to 3 nm, we find a distinct maximum in the tunnel magneto-Seebeck effect for 2.6 nm barrier thickness. This maximum is independently measured for two barrier materials, namely MgAl2O4 and MgO. Additionally, samples with an MgAl2O4 barrier exhibit a high thermovoltage of more than 350 µV in comparison to 90 µV for the MTJs with MgO barrier when heated with the maximum laser power of 150 mW. Our results allow for the fabrication of improved stacks when dealing with temperature differences across magnetic tunnel junctions for future applications in spin caloritronics, the emerging research field that combines spintronics and themoelectrics. arXiv:1706.08287v1 [cond-mat.mtrl-sci]

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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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Influence of the thermal interface resistance on the thermovoltage of a magnetic tunnel junction

Cited by 29 publications

References 19 publications

Impact of Joule heating on the stability phase diagrams of perpendicular magnetic tunnel junctions

Impact of Joule heating on the stability phase diagrams of perpendicular magnetic tunnel junctions

Enhancement of thermovoltage and tunnel magneto-Seebeck effect in CoFeB-based magnetic tunnel junctions by variation of the MgAl2O4 and MgO barrier thickness

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

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