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Journal Articles

Current-induced spin polarization on a Pt surface; A New approach using spin-polarized positron annihilation spectroscopy

Kawasuso, Atsuo; Fukaya, Yuki; Maekawa, Masaki; Zhang, H.; Seki, Takeshi*; Yoshino, Tatsuro*; Saito, Eiji*; Takanashi, Koki*

Journal of Magnetism and Magnetic Materials, 342, p.139 - 143, 2013/09

 Times Cited Count:19 Percentile:67.23(Materials Science, Multidisciplinary)

Transversely spin-polarized positrons were injected near Pt and Au surfaces under an applied electric current. The three-photon annihilation of spin-triplet positronium, which was emitted from the surfaces into vacuum, was observed. When the positron spin polarization was perpendicular to the current direction, the maximum asymmetry of the three-photon annihilation intensity was observed upon current reversal for the Pt surfaces, whereas it was significantly reduced for the Au surface. The experimental results suggest that electrons near the Pt surfaces were in-plane and transversely spin-polarized with respect to the direction of the electric current. The maximum electron spin polarization was estimated to be more than 0.01 (1%).

Journal Articles

Interface induced inverse spin Hall effect in bismuth/permalloy bilayer

Hou, D.*; Qiu, Z.*; Harii, Kazuya; Kajiwara, Yosuke*; Uchida, Kenichi*; Fujikawa, Yasunori*; Nakayama, Hiroyasu*; Yoshino, Tatsuro*; An, Toshu*; Ando, Kazuya*; et al.

Applied Physics Letters, 101(4), p.042403_1 - 042403_4, 2012/07

 Times Cited Count:60 Percentile:91.48(Physics, Applied)

Inverse spin Hall effect has been investigated in bismuth(Bi)/permalloy(Py) bilayer films by using the spin pumping at room temperature. From the ferromagnetic-resonance-spectrum linewidth data, Bi is proved to be a good spin sink in our structure. We measured inverse spin Hall voltage and conductance of the Bi/Py bilayer and found that the inverse spin Hall current, $$I_c$$, decreases with increasing the Bi thickness, which is in contrast to the former understanding in similar bilayer systems, e.g., Pt/Py. We constructed a model to explain the thickness dependence of $$I_c$$ quantitatively, in which spin transport modulation near Bi/Py interface is considered.

Journal Articles

Geometry dependence on inverse spin Hall effect induced by spin pumping in Ni$$_{81}$$Fe$$_{19}$$/Pt films

Nakayama, Hiroyasu*; Ando, Kazuya*; Harii, Kazuya; Yoshino, Tatsuro*; Takahashi, Ryo*; Kajiwara, Yosuke*; Uchida, Kenichi*; Fujikawa, Yasunori*; Saito, Eiji

Physical Review B, 85(14), p.144408_1 - 144408_7, 2012/04

 Times Cited Count:161 Percentile:97.96(Materials Science, Multidisciplinary)

Geometric effects on the inverse spin Hall effect (ISHE) induced by the spin pumping driven by the ferromagnetic resonance (FMR) have been investigated quantitatively. We measured the FMR spectra and the electromotive force induced by the ISHE with changing the size and the thickness in Ni$$_{81}$$Fe$$_{19}$$/Pt films. The intensity of generated charge currents due to the ISHE changes systematically with changing the film geometry. The experimental results show a clear difference between Ni$$_{81}$$Fe$$_{19}$$ and Pt thickness dependence of the ISHE induced by the spin pumping.

Journal Articles

All-oxide system for spin pumping

Qiu, Z.*; Kajiwara, Yosuke*; Ando, Kazuya*; Fujikawa, Yasunori*; Uchida, Kenichi*; Tashiro, Takaharu*; Harii, Kazuya*; Yoshino, Tatsuro*; Saito, Eiji

Applied Physics Letters, 100(2), p.022402_1 - 022402_3, 2012/01

 Times Cited Count:28 Percentile:76.85(Physics, Applied)

In a simple all-oxide system, spin pumping driven by spin wave resonances have been investigated by using the inverse spin-Hall effect (ISHE). In a lanthanum doped yttrium iron garnet (La:YIG)/indium tin oxide (ITO) bilayer film, the spin pumping generates and injects a spin current into the ITO layer, and an electromotive force signal is observed via the ISHE. The electromotive forces were measured depend on the out-of-plane magnetic-field-angle and the microwave excitation power, which were consistent with the theoretical prediction of the ISHE. The realization of the all-oxide spin pumping system extends possibilities for the oxide spintronics.

Journal Articles

Inverse spin-Hall effect induced by spin pumping in metallic systems

Ando, Kazuya*; Takahashi, Saburo; Ieda, Junichi; Kajiwara, Yosuke*; Nakayama, Hiroyasu*; Yoshino, Tatsuro*; Harii, Kazuya*; Fujikawa, Yasunori*; Matsuo, Mamoru*; Maekawa, Sadamichi; et al.

Journal of Applied Physics, 109(10), p.103913_1 - 103913_11, 2011/05

 Times Cited Count:338 Percentile:99.43(Physics, Applied)

The inverse spin-Hall effect (ISHE) induced by the spin pumping has been investigated systematically in simple ferromagnetic/paramagnetic bilayer systems. The spin pumping driven by ferromagnetic resonance injects a spin current into the paramagnetic layer, which gives rise to an electromotive force transverse to the spin current using the ISHE in the paramagnetic layer. In a Ni$$_{81}$$Fe$$_{19}$$/Pt film, we found an electromotive force perpendicular to the applied magnetic field at the ferromagnetic resonance condition. The spectral shape of the electromotive force is well reproduced using a simple Lorentz function, indicating that the electromotive force is due entirely to the ISHE induced by the spin pumping; the extrinsic magnetogalvanic effects are eliminated in this measurement. The electromotive force varies systematically by changing the microwave power, magnetic-field angle, and film size, which are well reproduced by a calculation based on the Landau-Lifshitz-Gilbert equation combined with the models of the ISHE and spin pumping. The electromotive force was observed also in a Pt/Y$$_3$$Fe$$_4$$GaO$$_{12}$$ film, in which the metallic Ni$$_{81}$$Fe$$_{19}$$ layer is replaced by an insulating Y$$_3$$Fe$$_4$$GaO$$_{12}$$ layer, supporting that the spin-pumping-induced ISHE is responsible for the observed electromotive force.

Journal Articles

Universality of the spin pumping in metallic bilayer films

Yoshino, Tatsuro*; Ando, Kazuya*; Harii, Kazuya*; Nakayama, Hiroyasu*; Kajiwara, Yosuke*; Saito, Eiji

Applied Physics Letters, 98(3), p.132503_1 - 132503_3, 2011/03

 Times Cited Count:30 Percentile:77.86(Physics, Applied)

We show a clear guideline for generating a large spin current using the spin pumping in metallic bilayer films. We measured spin currents generated by the spin pumping in Ni$$_{1-x}$$Fe$$_{x}$$/Pt bilayer films using the inverse spin-Hall effect (ISHE). The magnitude of the ISHE signals are well reproduced by a calculation based on the model of the spin pumping. The result shows that the amplitude of a spin current is universally determined by the product of the saturation magnetization, the additional damping constant, and the solid angle of the magnetization precession.

Journal Articles

Inverse spin-Hall effect induced by spin pumping in different size Ni$$_{81}$$Fe$$_{19}$$/Pt films

Nakayama, Hiroyasu*; Ando, Kazuya*; Harii, Kazuya*; Fujikawa, Yasunori*; Kajiwara, Yosuke*; Yoshino, Tatsuro*; Saito, Eiji

Journal of Physics; Conference Series, 266, p.012100_1 - 012100_4, 2011/01

 Times Cited Count:7 Percentile:96.03

The inverse spin-Hall effect, conversion of spin currents into electric voltage, has been investigated in Ni$$_{81}$$Fe$$_{19}$$/Pt bilayer films with different length and width. We measured the electric voltage generated by the inverse spin-Hall effect induced by the spin pumping at room temperature. The experimental results indicate that the electric voltage induced by the inverse spin-Hall effect is proportional to the length of Ni$$_{81}$$Fe$$_{19}$$/Pt bilayer films. In contrast, the electric voltage exhibits almost no variation by changing the width of the Ni$$_{81}$$Fe$$_{19}$$/Pt films. These results are consistent with the inverse spin-Hall effect model.

Journal Articles

Spin pumping and magnetization-precession trajectory in thin film systems

Nonaka, Tatsumi*; Ando, Kazuya*; Yoshino, Tatsuro*; Saito, Eiji

Journal of Physics; Conference Series, 266, p.012101_1 - 012101_5, 2011/01

 Times Cited Count:0 Percentile:0.01

The spin pumping, generation of spin currents from magnetization precession, has been investigated in terms of the trajectory of magnetization precession in thin film systems. By using the Landau-Lifshitz-Gilbert equation combined with the model of the spin pumping, we found that the magnitude of the spin current generated by the spin pumping is determined by the elliptical orbit area of magnetization precession, which is maximized when the external magnetic field is applied oblique to the film plane.

Journal Articles

Quantifying spin mixing conductance in $$F$$/Pt ($$F$$ = Ni, Fe, and Ni$$_{81}$$Fe$$_{19}$$) bilayer film

Yoshino, Tatsuro*; Ando, Kazuya*; Harii, Kazuya*; Nakayama, Hiroyasu*; Kajiwara, Yosuke*; Saito, Eiji

Journal of Physics; Conference Series, 266, p.012115_1 - 012115_4, 2011/01

 Times Cited Count:10 Percentile:97.9

The spin-mixing conductances in $$F$$/Pt ($$F$$ = Ni, Fe, and Ni$$_{81}$$Fe$$_{19}$$) bilayer films were quantified from the peak-to-peak linewidth of ferromagnetic resonance (FMR) spectra based on the model of the spin pumping. When the Pt layer is attached to the $$F$$ layer, we found the enhancement of the FMR linewidth due to the spin pumping. The experimental results show that the spin-mixing conductances in $$F$$/Pt ($$F$$ = Ni, Fe, and Ni$$_{81}$$Fe$$_{19}$$) bilayer films have the same order of magnitude, showing that spin injection efficiency in the spin pumping is almost identical in these films.

Oral presentation

Observation of spin-Hall effect using spin-polarized positron annihilation

Fukaya, Yuki; Maekawa, Masaki; Yabuuchi, Atsushi; Mochizuki, Izumi; Saito, Eiji; Yoshino, Tatsuro*; Kawasuso, Atsuo

no journal, , 

no abstracts in English

Oral presentation

Direct detection of spin-Hall effect using spin-polarized positron annihilation

Fukaya, Yuki; Maekawa, Masaki; Yabuuchi, Atsushi; Mochizuki, Izumi; Yoshino, Tatsuro*; Saito, Eiji; Kawasuso, Atsuo

no journal, , 

no abstracts in English

Oral presentation

Observation of spin-Hall effects using spin-polarized positron beam

Fukaya, Yuki; Maekawa, Masaki; Mochizuki, Izumi; Seki, Takeshi*; Takanashi, Koki*; Yoshino, Tatsuro*; Saito, Eiji; Kawasuso, Atsuo

no journal, , 

no abstracts in English

Oral presentation

Spin-Hall effect studied by spin-polarized positron annihilation

Fukaya, Yuki; Zhang, H.; Maekawa, Masaki; Mochizuki, Izumi; Seki, Takeshi*; Takanashi, Koki*; Yoshino, Tatsuro*; Saito, Eiji; Ieda, Junichi; Maekawa, Sadamichi; et al.

no journal, , 

no abstracts in English

Oral presentation

Spin polarization of Pt/Fe/MgO and Pt/MgO surfaces studied by spin-polarized positron beam

Zhang, H.; Fukaya, Yuki; Maekawa, Masaki; Li, H.; Kawasuso, Atsuo; Seki, Takeshi*; Yoshino, Tatsuro*; Saito, Eiji*; Takanashi, Koki*

no journal, , 

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