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Probing Spin Accumulation induced Magnetocapacitance in a Single Electron Transistor.

Lee TH, Chen CD - Sci Rep (2015)

Bottom Line: The latter is known as the magnetocapacitance effect.This dipole can effectively give rise to an additional serial capacitance, which represents an extra charging energy that the tunneling electrons would encounter.It is found that the extra threshold energy is experienced only by electrons entering the islands, bringing about asymmetry in the measured Coulomb diamond.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, National Taiwan University, Taipei 106, Taiwan.

ABSTRACT
The interplay between spin and charge in solids is currently among the most discussed topics in condensed matter physics. Such interplay gives rise to magneto-electric coupling, which in the case of solids was named magneto-electric effect, as predicted by Curie on the basis of symmetry considerations. This effect enables the manipulation of magnetization using electrical field or, conversely, the manipulation of electrical polarization by magnetic field. The latter is known as the magnetocapacitance effect. Here, we show that non-equilibrium spin accumulation can induce tunnel magnetocapacitance through the formation of a tiny charge dipole. This dipole can effectively give rise to an additional serial capacitance, which represents an extra charging energy that the tunneling electrons would encounter. In the sequential tunneling regime, this extra energy can be understood as the energy required for a single spin to flip. A ferromagnetic single-electron-transistor with tunable magnetic configuration is utilized to demonstrate the proposed mechanism. It is found that the extra threshold energy is experienced only by electrons entering the islands, bringing about asymmetry in the measured Coulomb diamond. This asymmetry is an unambiguous evidence of spin accumulation induced tunnel magnetocapacitance, and the measured magnetocapacitance value is as high as 40%.

No MeSH data available.


Measured Coulomb diamonds in 4 different alignment configurations.The diamonds are presented in color intensity plots in (b) and are stacked together for comparison in (a). In (b), the dashed lines mark the borders of Coulomb diamonds, and their slopes are used to evaluate effective junction capacitances.
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f2: Measured Coulomb diamonds in 4 different alignment configurations.The diamonds are presented in color intensity plots in (b) and are stacked together for comparison in (a). In (b), the dashed lines mark the borders of Coulomb diamonds, and their slopes are used to evaluate effective junction capacitances.

Mentions: Clear stability diagrams were also obtained for the other three configurations. It is interesting to note that the diamond can become asymmetric in these configurations. To clearly depict the deviation in each alignment configuration, four diamonds are stacked altogether in Fig. 2a. The four borders of these diamonds are indicated by Lin, Rout, Lout, and Rin. L and R stand for tunneling taking place at the left and right junctions, respectively; while the subscription denotes the electron tunneling direction in respect to the island. In the Right-AP configuration the Lout border tilts clockwise, while in the Left-AP configuration the Rout border tilts anti-clockwise. In Both-AP, the two borders tilts to overlap with both the Lout of Right-AP and the Rout of Left-AP. The change in the border slopes in these three configurations signifies a change in the junction capacitance. We recall that, in an SET, the threshold for electrons to tunnel, i.e. the border, through a junction is determined by the capacitance of the counterpart junction. A smaller capacitance corresponds to a more outwardly tilted border. Hence, our observations in Fig. 2 can be summarized as follows: when tunneling out from the island through a junction, the electrons experience a decrease in the capacitance of the counterpart junction, if and only if the counterpart junction is in AP configuration. This condition of a decrease in the capacitance seen by the tunneling electrons is referred to as the TMC criterion.


Probing Spin Accumulation induced Magnetocapacitance in a Single Electron Transistor.

Lee TH, Chen CD - Sci Rep (2015)

Measured Coulomb diamonds in 4 different alignment configurations.The diamonds are presented in color intensity plots in (b) and are stacked together for comparison in (a). In (b), the dashed lines mark the borders of Coulomb diamonds, and their slopes are used to evaluate effective junction capacitances.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4562261&req=5

f2: Measured Coulomb diamonds in 4 different alignment configurations.The diamonds are presented in color intensity plots in (b) and are stacked together for comparison in (a). In (b), the dashed lines mark the borders of Coulomb diamonds, and their slopes are used to evaluate effective junction capacitances.
Mentions: Clear stability diagrams were also obtained for the other three configurations. It is interesting to note that the diamond can become asymmetric in these configurations. To clearly depict the deviation in each alignment configuration, four diamonds are stacked altogether in Fig. 2a. The four borders of these diamonds are indicated by Lin, Rout, Lout, and Rin. L and R stand for tunneling taking place at the left and right junctions, respectively; while the subscription denotes the electron tunneling direction in respect to the island. In the Right-AP configuration the Lout border tilts clockwise, while in the Left-AP configuration the Rout border tilts anti-clockwise. In Both-AP, the two borders tilts to overlap with both the Lout of Right-AP and the Rout of Left-AP. The change in the border slopes in these three configurations signifies a change in the junction capacitance. We recall that, in an SET, the threshold for electrons to tunnel, i.e. the border, through a junction is determined by the capacitance of the counterpart junction. A smaller capacitance corresponds to a more outwardly tilted border. Hence, our observations in Fig. 2 can be summarized as follows: when tunneling out from the island through a junction, the electrons experience a decrease in the capacitance of the counterpart junction, if and only if the counterpart junction is in AP configuration. This condition of a decrease in the capacitance seen by the tunneling electrons is referred to as the TMC criterion.

Bottom Line: The latter is known as the magnetocapacitance effect.This dipole can effectively give rise to an additional serial capacitance, which represents an extra charging energy that the tunneling electrons would encounter.It is found that the extra threshold energy is experienced only by electrons entering the islands, bringing about asymmetry in the measured Coulomb diamond.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, National Taiwan University, Taipei 106, Taiwan.

ABSTRACT
The interplay between spin and charge in solids is currently among the most discussed topics in condensed matter physics. Such interplay gives rise to magneto-electric coupling, which in the case of solids was named magneto-electric effect, as predicted by Curie on the basis of symmetry considerations. This effect enables the manipulation of magnetization using electrical field or, conversely, the manipulation of electrical polarization by magnetic field. The latter is known as the magnetocapacitance effect. Here, we show that non-equilibrium spin accumulation can induce tunnel magnetocapacitance through the formation of a tiny charge dipole. This dipole can effectively give rise to an additional serial capacitance, which represents an extra charging energy that the tunneling electrons would encounter. In the sequential tunneling regime, this extra energy can be understood as the energy required for a single spin to flip. A ferromagnetic single-electron-transistor with tunable magnetic configuration is utilized to demonstrate the proposed mechanism. It is found that the extra threshold energy is experienced only by electrons entering the islands, bringing about asymmetry in the measured Coulomb diamond. This asymmetry is an unambiguous evidence of spin accumulation induced tunnel magnetocapacitance, and the measured magnetocapacitance value is as high as 40%.

No MeSH data available.