An update on the thermodynamics of Ta2O5

Jacob, Κ. T.; Shekhar, Chander; Waseda, Yoshio

doi:10.1016/j.jct.2008.12.006

Cited by 48 publications

(30 citation statements)

References 34 publications

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“…To consider the efficient thermal flux out of the device via the gold TC also the outer boundary of the TC on the right hand side was set to 300 K. The thermal properties of all components of the MTJ stack are based on literature values as given in Table I. 15,17,18,19,20,21,22,23 Whenever available, thin film values of relevant parameters were used. Otherwise bulk values were considered as marked in the table.…”

Section: Articlementioning

confidence: 99%

Determination of spin-dependent Seebeck coefficients of CoFeB/MgO/CoFeB magnetic tunnel junction nanopillars

Liebing

Serrano-Guisan

Rott

et al. 2012

Journal of Applied Physics

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We investigate the spin-dependent Seebeck coefficient and the tunneling magneto thermopower of CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJ) in the presence of thermal gradients across the MTJ. Thermal gradients are generated by an electric heater on top of the nanopillars. The thermo power voltage V TP across the MTJ is found to scale linearly with the heating power and reveals similar field dependence as the tunnel magnetoresistance.The amplitude of the thermal gradient is derived from calibration measurements in combination with finite element simulations of the heat flux. Based on this, large spindependent Seebeck coefficients of the order of (240 ± 110) µV/K are derived. From additional measurements on MTJs after dielectric breakdown, a tunneling magneto thermopower up to 90% can be derived for 1.5 nm MgO based MTJ nanopillars.

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Section: Articlementioning

confidence: 99%

Determination of spin-dependent Seebeck coefficients of CoFeB/MgO/CoFeB magnetic tunnel junction nanopillars

Liebing

Serrano-Guisan

Rott

et al. 2012

Journal of Applied Physics

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“…The study of the physical and chemical properties of Ta 2 O 5 films is of great importance not only from the technological per-spective but also from the scientific one. In previous research the existence of several polymorphs 15,16 were established and although most researchers agree that the system crystallizes in either hexagonal (δ phase) or orthorhombic (β phase) structures, the ground-state crystal structure is still under investigation 17,18 . The atomic structure and the properties of Ta 2 O 5 strongly depend on the fabrication methods.…”

Section: Introductionmentioning

confidence: 99%

Effect of ion bombardment on the chemical properties of crystalline tantalum pentoxide films

Pérez

Sosa

Perera

et al. 2019

Vacuum

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The effect of argon ion bombardment on the chemical properties of crystalline Ta2O5 films grown on Si(100) substrates by radio frequency magnetron sputtering was investigated by X-ray photoelectron spectroscopy. All samples were irradiated for several time intervals [(0.5, 3, 6, 9) min] and the Ta 4f and O 1s core levels were measured each time. Upon analysis at the surface of the films, we observe the Ta 4f spectrum characteristic of Ta2O5. Irradiated samples exhibit the formation of Ta suboxides with oxidation states Ta 1+ , Ta 2+ , Ta 3+ , Ta 4+ , and Ta 5+ . Exposing the films, after ion bombardment, to ambient for some days stimulates the amorphous phase of Ta2O5 at the surface suggesting that the suboxides of Ta are unstable. Using a sputtering simulation we discuss that these suboxides are largely generated during ion bombardment that greatly reduces the oxygen to tantalum ratio as the irradiation time increases. The computer simulation indicates that this is due to the high sputtering yield of oxygen.

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“…However, as stated in section 3.2, the laser power transmitted through the Au layer does not exceed 1%. Taking into account the low thermal conductivity and high heat capacity of Ta 2 O 5[25,26], the heat is not conducted to the bottom Ta layer, which could pass it on to the bottom CoFeB electrode.…”

mentioning

confidence: 99%

Pumping laser excited spins through MgO barriers

Martens

Walowski

Schumann

et al. 2017

J. Phys. D: Appl. Phys.

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We present a study of the tunnel magneto-Seebeck (TMS) 1 effect in MgO based magnetic tunnel junctions (MTJs). The electrodes consist of CoFeB with inplane magnetic anisotropy. The temperature gradients which generate a voltage across the MTJs layer stack are created using laser heating. Using this method, the temperature can be controlled on the micrometer length scale: here, we investigate, how both, the TMS voltage and the TMS effect, depend on the size, position and intensity of the applied laser spot. For this study, a large variety of different temperature distributions was created across the junction. We recorded twodimensional maps of voltages generated by heating in dependence of the laser spot position and the corresponding calculated TMS values. The voltages change in value and sign, from large positive values when heating the MTJ directly in the centre to small values when heating the junction on the edges and even small negative values when heating the sample away from the junction. Those zero crossings lead to very high calculated TMS ratios. Our systematic analysis shows, that the distribution of the temperature gradient is essential, to achieve high voltage signals and reasonable resulting TMS ratios. Furthermore, artefacts on the edges produce misleading results, but also open up further possibilities of more complex heating scenarios for spincaloritronics in spintronic devices.

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An update on the thermodynamics of Ta2O5

Cited by 48 publications

References 34 publications

Determination of spin-dependent Seebeck coefficients of CoFeB/MgO/CoFeB magnetic tunnel junction nanopillars

Determination of spin-dependent Seebeck coefficients of CoFeB/MgO/CoFeB magnetic tunnel junction nanopillars

Effect of ion bombardment on the chemical properties of crystalline tantalum pentoxide films

Pumping laser excited spins through MgO barriers

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