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Significant change of spin transport property in Cu/Nb bilayer due to superconducting transition.

Ohnishi K, Ono Y, Nomura T, Kimura T - Sci Rep (2014)

Bottom Line: To observe such SC spin transports, the suppression of the extrinsic effects originating from the heating and Oersted field due to the electric current is a crucial role.Pure spin current without accompanying the charge current is known as a powerful mean for preventing such extrinsic effects.By using this ideal platform, we found that the spin absorption is strongly suppressed by the SC transition of Nb.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Physics, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan [2] Research Center for Quantum Nano-Spin Sciences, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan.

ABSTRACT
The combination between the spin-dependent and super-conducting (SC) transports is expected to provide intriguing properties such as crossed Andreev reflection and spin-triplet superconductivity. This may be able to open a new avenue in the field of spintronics, namely superconducting spintronics because a superconductor itself has great potential for future nanoelectronic applications. To observe such SC spin transports, the suppression of the extrinsic effects originating from the heating and Oersted field due to the electric current is a crucial role. Pure spin current without accompanying the charge current is known as a powerful mean for preventing such extrinsic effects. However, non-negligible heat flow is found to exist even in a conventional pure spin current device based on laterally-configured spin valve because of the heating around the spin injector. Here, we develop a nanopillar-based lateral spin valve, which significantly reduces the heat generation, on a superconducting Nb film. By using this ideal platform, we found that the spin absorption is strongly suppressed by the SC transition of Nb. This demonstration is the clear evidence that the super-conducting Nb is an insulator for the pure spin current.

No MeSH data available.


Related in: MedlinePlus

(a) Nonlocal spin valve curve measured at 10 K in the nanopillar based Py/Cu lateral spin valve without the Nb layer together with the probe configuration for the measurement (right). Nonlocal spin valve curves measured at 10 K (NC state) (b) and 2.3 K (SC state) (c) together with the respective probe configurations.
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f3: (a) Nonlocal spin valve curve measured at 10 K in the nanopillar based Py/Cu lateral spin valve without the Nb layer together with the probe configuration for the measurement (right). Nonlocal spin valve curves measured at 10 K (NC state) (b) and 2.3 K (SC state) (c) together with the respective probe configurations.

Mentions: We then evaluated the spin transport by mean of the nonlocal spin valve measurement using the Py nanopillars. Here, the injection of the spin-polarized electrons from the Py nanopillar (Py1) into the Cu/Nb bilayer produces the spin current both in the left-hand and right-hand side. The pure spin current is produced in the right-hand side, and can be detected by measuring the electrical voltage using another Py nanopillar (Py2)32. The voltage difference between parallel and anti-parallel states divided by the injecting current is known as a spin signal. The detected spin signal reflects the magnitude of the spin current at the Py2/Cu interface. Before showing the results in the bilayer film, we show a typical nonlocal spin valve signal in the Py/Cu nanopillar lateral spin valve without Nb layer in Fig. 3(a), as a reference. A spin signal with the magnitude of 0.85 mΩ was clearly observed at 10 K. The spatial homogeneity of the spin injection using the Py nanopillar was evaluated by changing the current- and voltage-probe positions in the nonmagnetic channels. We confirmed that the obtained spin signals in two configurations are almost same. This indicates that the Py nanopillar produce the homogeneous spin accumulation underneath the injecting electrode. In the Cu/Nb bilayer film, since the spin relaxation process in the Cu channel is affected by the electron conducting state in the Nb, the spin signal should be modified from that in the reference sample34. In addition, the significant change should be observed in the spin signal by the transition from the NC to the SC in the Nb layer.


Significant change of spin transport property in Cu/Nb bilayer due to superconducting transition.

Ohnishi K, Ono Y, Nomura T, Kimura T - Sci Rep (2014)

(a) Nonlocal spin valve curve measured at 10 K in the nanopillar based Py/Cu lateral spin valve without the Nb layer together with the probe configuration for the measurement (right). Nonlocal spin valve curves measured at 10 K (NC state) (b) and 2.3 K (SC state) (c) together with the respective probe configurations.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4151101&req=5

f3: (a) Nonlocal spin valve curve measured at 10 K in the nanopillar based Py/Cu lateral spin valve without the Nb layer together with the probe configuration for the measurement (right). Nonlocal spin valve curves measured at 10 K (NC state) (b) and 2.3 K (SC state) (c) together with the respective probe configurations.
Mentions: We then evaluated the spin transport by mean of the nonlocal spin valve measurement using the Py nanopillars. Here, the injection of the spin-polarized electrons from the Py nanopillar (Py1) into the Cu/Nb bilayer produces the spin current both in the left-hand and right-hand side. The pure spin current is produced in the right-hand side, and can be detected by measuring the electrical voltage using another Py nanopillar (Py2)32. The voltage difference between parallel and anti-parallel states divided by the injecting current is known as a spin signal. The detected spin signal reflects the magnitude of the spin current at the Py2/Cu interface. Before showing the results in the bilayer film, we show a typical nonlocal spin valve signal in the Py/Cu nanopillar lateral spin valve without Nb layer in Fig. 3(a), as a reference. A spin signal with the magnitude of 0.85 mΩ was clearly observed at 10 K. The spatial homogeneity of the spin injection using the Py nanopillar was evaluated by changing the current- and voltage-probe positions in the nonmagnetic channels. We confirmed that the obtained spin signals in two configurations are almost same. This indicates that the Py nanopillar produce the homogeneous spin accumulation underneath the injecting electrode. In the Cu/Nb bilayer film, since the spin relaxation process in the Cu channel is affected by the electron conducting state in the Nb, the spin signal should be modified from that in the reference sample34. In addition, the significant change should be observed in the spin signal by the transition from the NC to the SC in the Nb layer.

Bottom Line: To observe such SC spin transports, the suppression of the extrinsic effects originating from the heating and Oersted field due to the electric current is a crucial role.Pure spin current without accompanying the charge current is known as a powerful mean for preventing such extrinsic effects.By using this ideal platform, we found that the spin absorption is strongly suppressed by the SC transition of Nb.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Physics, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan [2] Research Center for Quantum Nano-Spin Sciences, Kyushu University, 6-10-1 Hakozaki, Fukuoka 812-8581, Japan.

ABSTRACT
The combination between the spin-dependent and super-conducting (SC) transports is expected to provide intriguing properties such as crossed Andreev reflection and spin-triplet superconductivity. This may be able to open a new avenue in the field of spintronics, namely superconducting spintronics because a superconductor itself has great potential for future nanoelectronic applications. To observe such SC spin transports, the suppression of the extrinsic effects originating from the heating and Oersted field due to the electric current is a crucial role. Pure spin current without accompanying the charge current is known as a powerful mean for preventing such extrinsic effects. However, non-negligible heat flow is found to exist even in a conventional pure spin current device based on laterally-configured spin valve because of the heating around the spin injector. Here, we develop a nanopillar-based lateral spin valve, which significantly reduces the heat generation, on a superconducting Nb film. By using this ideal platform, we found that the spin absorption is strongly suppressed by the SC transition of Nb. This demonstration is the clear evidence that the super-conducting Nb is an insulator for the pure spin current.

No MeSH data available.


Related in: MedlinePlus