SRPES and XPS analysis of activation and deterioration processes for Ti-Zr-V NEG coating

Kamiya, Junichiro; Abe, Kazuhide; Fujimori, Shinichi; Fukuda, Tatsuo; Kobata, Masaaki; Morohashi, Yuko; Tsuda, Yasutaka; Yamada, Ippei; Yoshigoe, Akitaka

e-Journal of Surface Science and Nanotechnology (Internet), 22(4), p.316 - 326, 2024/08

https://doi.org/10.1380/ejssnt.2024-030

The activation and deterioration mechanisms of the Ti-Zr-V non-evaporable getter (NEG) coating have been investigated. Operando analysis of the surface chemical composition change of the Ti-Zr-V coating was performed by the synchrotron radiation photoelectron spectroscopy (SRPES) during the process of raising the sample temperature to 250C, corresponding to the activation process of NEG coating. The surface oxidation process was also characterized by the SRPES during the injection of O_2 gas into the chamber while keeping the sample temperature at 250C, corresponding to the deterioration process of NEG coating, i.e. surface oxidation and oxygen diffusion to the coating interior. The depth profile of the oxidized sample was measured with X-ray photoelectron spectroscopy. The results shows, in the activation process, the surface Zr gets the oxygen from the oxides of Ti and V at the first stage, resulting in the metallic Ti and V on the surface, and the oxygen of the Zr-oxide and/or Zr sub-oxides diffuse to the interior of the coating in the continuous temperature rise, resulting in the metallic Zr on the surface. It is further suggested that the deterioration of the Ti-Zr-V NEG coating means the Zr and secondary Ti are oxidized deep into the coating, resulting in the restriction of the oxygen migration from the NEG compositions on the surface and consequently the lack of surface metallization.

Intrinsic surface magnetic anisotropy in YFeO as the origin of low-magnetic-field behavior of the spin Seebeck effect

Uchida, Kenichi*; Oe, Junichiro*; Kikkawa, Takashi*; Daimon, Shunsuke*; Hou, D.*; Qiu, Z.*; Saito, Eiji

Physical Review B, 92(1), p.014415_1 - 014415_8, 2015/07

https://doi.org/10.1103/PhysRevB.92.014415

Unidirectional spin-wave heat conveyer

An, Toshu*; Vasyuchka, V. I.*; Uchida, Kenichi*; Chumak, A. V.*; Yamaguchi, Kazuya*; Harii, Kazuya; Oe, Junichiro*; Jungfleisch, M. B.*; Kajiwara, Yosuke*; Adachi, Hiroto; et al.

Nature Materials, 12(6), p.549 - 553, 2013/06

https://doi.org/10.1038/nmat3628

Time-domain observation of the spinmotive force in permalloy nanowires

Hayashi, Masamitsu*; Ieda, Junichi; Yamane, Yuta; Oe, Junichiro*; Takahashi, Yukiko*; Mitani, Seiji*; Maekawa, Sadamichi

Physical Review Letters, 108(14), p.147202_1 - 147202_5, 2012/04

https://doi.org/10.1103/PhysRevLett.108.147202

Spinmotive force associated with a moving domain wall is observed directly in permalloy nanowires using real time voltage measurements with proper subtraction of the electromotive force. Whereas the wall velocity exhibits nonlinear dependence on a magnetic field, the generated voltage increases linearly with the field. We show that the sign of the voltage reverses when the wall propagation direction is altered. Numerical simulations explain quantitatively these features of spinmotive force and indicate that the spinmotive force scales with the field even in a field range where the wall motion is no longer associated with periodic structure transformation.

Spinmotive force due to intrinsic energy of ferromagnetic nanowires

Yamane, Yuta; Ieda, Junichi; Oe, Junichiro*; Barnes, S. E.*; Maekawa, Sadamichi

Applied Physics Express, 4(9), p.093003_1 - 093003_3, 2011/09

https://doi.org/10.1143/APEX.4.093003

Numerical study on the spin Seebeck effect

Oe, Junichiro; Adachi, Hiroto; Takahashi, Saburo; Maekawa, Sadamichi

Physical Review B, 83(11), p.115118_1 - 115118_5, 2011/03

https://doi.org/10.1103/PhysRevB.83.115118

Thermally driven spin-wave spin currents in ferromagnetic (FM) materials and a resulting measurable electric signal in a normal metal (NM) probe placed on FM are theoretically investigated. We develop the numerical technique for calculating a spin Seebeck signal detected by the NM probe that converts the spin current to the charge current. By taking into account the fluctuation-dissipation theorem for thermally fluctuating spins at the interface of a FM/NM junction, the spin current is induced in the NM probe via an exchange interaction when the FM feels the temperature gradient. Numerical simulation clarifies the role of the sample boundary on the spatial distribution of the spin current both in FM and NM. The spin-wave spin current that flows parallel to the heat current is also investigated.

Gigantic enhancement of spin Seebeck effect by phonon drag

Adachi, Hiroto; Uchida, Kenichi*; Saito, Eiji; Oe, Junichiro; Takahashi, Saburo; Maekawa, Sadamichi

Applied Physics Letters, 97(25), p.252506_1 - 252506_3, 2010/12

https://doi.org/10.1063/1.3529944

We investigate both theoretically and experimentally a gigantic enhancement of the spin Seebeck effect in a prototypical magnet LaYFeO at low temperatures. Our theoretical analysis sheds light on the important role of phonons: the spin Seebeck effect is enormously enhanced by nonequilibrium phonons that drag low-lying spin excitations. We further argue that this scenario gives a clue to understand the observation of the spin Seebeck effect that is unaccompanied by a global spin current, and predict that the substrate condition affects the observed signal.

New numerical approach for studying diluted magnetic semiconductors

Oe, Junichiro; Gu, B.; Maekawa, Sadamichi

Kotai Butsuri, 45(5), p.269 - 278, 2010/06

http://ci.nii.ac.jp/naid/40017190872

We report a new combined numerical approach for studying diluted magnetic semiconductors (DMS). In this approach, realistic parameters obtained by the calculation are used for performing quantum Monte Carlo calculations. We show that the proposed approach well describes the magnetic properties of DMS and can be used for designing the new DMS materials which has high Curie temperatures.

Analysis of activation and deterioration mechanism of Ti-Zr-V NEG coating by XPS

Kamiya, Junichiro; Abe, Kazuhide; Kobata, Masaaki; Tsuda, Yasutaka; Fukuda, Tatsuo; Fujimori, Shinichi; Morohashi, Yuko; Yamada, Ippei; Yoshigoe, Akitaka

no journal, , 

Sequence measurements with XPS have been performed to understand more detail about the activation and deterioration mechanism. The sample of a titanium plate with Ti-Zr-V coating of 1 um thickness was prepared. The sample was set in the surface science station in the BL23SU of SPring-8. At first, the XPS measurements for the sample surface were performed during the sample temperature was raised to 250C. After that, the XPS was subsequently performed during the injection of oxygen gas into the chamber while keeping the sample temperature at 250C, which corresponds to the accelerated deterioration test. After that, the depth profile of the sample was measured with another XPS apparatus with an X-ray tube by argon etching. The result showed that the surface Zr gets the oxygen from Ti oxide and V oxide at the first stage of the activation and the oxygen of the Zr oxide would diffuse to the bulk in the continuous temperature rise. It was revealed that the concentrated oxygen in the coating exists in the forms of mainly Zr oxide and Ti oxide in the second place.

Numerical study on the thermally driven spin-wave spin current

Oe, Junichiro; Adachi, Hiroto; Takahashi, Saburo; Maekawa, Sadamichi

no journal, , 

Recently, the relation between the heat current and the spin current has much attracted from the view of the spintronics applications. The heat current induces the spin current, the spin Seebeck effect, has been discovered not only inferromagnetic metals but also in ferromagnetic semiconductors and ferromagnetic insulators. In this reports, we investigate the spin Seebeck effect by using the numerical simulation. We focus on the dynamics of the magnetization in the presence of the fluctuating torque which represents finite temperatures. The spin current is driven by the magnetization dynamics and converted to the charge current in a normal metal probe. We use the Landau-Lifshitz-Gilbert equation for calculating the magnetization dynamics and the diffusion equation for the dynamics of the conduction electrons. Our results show good agreement with the experimental results qualitatively.