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Journal Articles

Three-dimensional bulk Fermi surfaces and Weyl crossings of Co$$_2$$MnGa thin films underneath a protection layer

Kono, Takashi*; Kakoki, Masaaki*; Yoshikawa, Tomoki*; Wang, X.*; Sumida, Kazuki; Muro, Takayuki*; Goto, Kazuki*; Sakuraba, Yuya*; Umetsu, Rie*; Kimura, Akio*

Physical Review B, 104(19), p.195112_1 - 195112_8, 2021/11

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

Angle-resolved photoelectron spectroscopy utilizing soft X-ray synchrotron radiation was applied to Heusler-type Co$$_2$$MnGa thin films that have a 1-nm Al capping layer. The bulk Fermi surfaces and band structures varied along the out-of-plane momentum, stemming from the three-dimensional crystal structure, in the absence of any in situ surface treatment. In addition, there were characteristic intersecting bands (Weyl cones), with crossing points near the Fermi level, which were consistent with computed results. The Weyl cones are of bulk origin and are responsible for the high anomalous Nernst and the anomalous Hall coefficients. A close comparison of the experimental band structures in Co$$_2$$MnGe and Co$$_2$$MnGa indicated that the rigid band picture is valid in both alloys and that fine carrier tuning is possible by replacing Ga with Ge to improve the anomalous conductivity.

Journal Articles

Spin-polarized Weyl cones and giant anomalous Nernst effect in ferromagnetic Heusler films

Sumida, Kazuki; Sakuraba, Yuya*; Masuda, Keisuke*; Kono, Takashi*; Kakoki, Masaaki*; Goto, Kazuki*; Zhou, W.*; Miyamoto, Koji*; Miura, Yoshio*; Okuda, Taiichi*; et al.

Communications Materials (Internet), 1, p.89_1 - 89_9, 2020/11

Journal Articles

Unveiling spin-dependent unoccupied electronic states of Co$$_{2}$$MnGe (Ga) film via Ge (Ga) $$L_{2,3}$$ absorption spectroscopy

Yoshikawa, Tomoki*; Antonov, V. N.*; Kono, Takashi*; Kakoki, Masaaki*; Sumida, Kazuki; Miyamoto, Koji*; Takeda, Yukiharu; Saito, Yuji; Goto, Kazuki*; Sakuraba, Yuya*; et al.

Physical Review B, 102(6), p.064428_1 - 064428_7, 2020/08

 Times Cited Count:1 Percentile:11.18(Materials Science, Multidisciplinary)

Journal Articles

Element-specific density of states of Co$$_{2}$$MnGe revealed by resonant photoelectron spectroscopy

Kono, Takashi*; Kakoki, Masaaki*; Yoshikawa, Tomoki*; Wang, X.*; Sumida, Kazuki*; Miyamoto, Koji*; Muro, Takayuki*; Takeda, Yukiharu; Saito, Yuji; Goto, Kazuki*; et al.

Physical Review B, 100(16), p.165120_1 - 165120_6, 2019/10

 Times Cited Count:4 Percentile:31.11(Materials Science, Multidisciplinary)

Journal Articles

Spin pumping efficiency from half metallic Co$$_2$$MnSi

Chudo, Hiroyuki; Ando, Kazuya*; Saito, Kesami*; Okayasu, Satoru; Haruki, Rie; Sakuraba, Yuya*; Yasuoka, Hiroshi; Takanashi, Koki; Saito, Eiji

Journal of Applied Physics, 109(7), p.073915_1 - 073915_4, 2011/04

 Times Cited Count:19 Percentile:63.39(Physics, Applied)

We present spin pumping using a Heusler alloy Co$$_2$$MnSi/Pt bilayer film. A spin current is produced by a ferromagnetic resonance (FMR) technique. The pure spin current injected into the Pt layer from the Co$$_2$$MnSi layer is detected by the inverse spin-Hall effect (ISHE), which converts the spin current into an electric current. We estimated a damping constant of the Co$$_2$$MnSi/Pt bilayer film from an angular dependence of FMR spectra. Using the damping constant efficiency of spin pumping from the Co$$_2$$MnSi layer is evaluated. We found that a mixing conductance at the Co$$_2$$MnSi/Pt interface is comparable to that at a permalloy/Pt interface.

Oral presentation

Spin pumping in Co$$_2$$MnSi

Chudo, Hiroyuki; Ando, Kazuya*; Saito, Kesami*; Okayasu, Satoru; Haruki, Rie; Sakuraba, Yuya*; Yasuoka, Hiroshi; Takanashi, Koki; Saito, Eiji

no journal, , 

no abstracts in English

Oral presentation

UHV-CVD growth of graphene for spintronic applications

Entani, Shiro; Matsumoto, Yoshihiro; Otomo, Manabu; Sakuraba, Yuya*; Avramov, P.; Naramoto, Hiroshi*; Takanashi, Koki; Sakai, Seiji

no journal, , 

Oral presentation

An Attempt to measure spin-polarization of Heusler alloy Co$$_{2}$$MnSi using spin-polarized positron annihilation

Kawasuso, Atsuo; Sakuraba, Yuya*; Fukaya, Yuki; Zhang, H.; Maekawa, Masaki; Mochizuki, Izumi; Takanashi, Koki*

no journal, , 

We are attempting to determine the spin-polarization of the Heusler alloys using spin-polarized positron annihilation spectroscopy. Positrons implanted near the surface combine with electrons to form positronium (Ps). From the o-Ps (spin triplet state) fraction, one can determine the electron spin-polarization. The samples used in this study are Co$$_{2}$$MnSi films grown on MgO(001) substrates. To avoid the surface oxidation, the sample surfaces are capped with Au thin layers (0.5 nm thick). The electron polarization are obtained to be 0.26. This is significantly smaller than that determined by using the Andreev reflection method. The further study using samples without any cap layers are needed.

Oral presentation

Materials design and characterization of nano-carbons for spintronic applications

Sakai, Seiji; Matsumoto, Yoshihiro; Entani, Shiro; Otomo, Manabu; Sorokin, B. P.*; Avramov, P.; Naramoto, Hiroshi*; Sakuraba, Yuya*; Takanashi, Koki

no journal, , 

no abstracts in English

Oral presentation

Spin-polarization of the Heusler type half-metals evaluated by spin-polarized positron annihilation

Kawasuso, Atsuo; Sakuraba, Yuya*; Zhang, H.; Maekawa, Masaki; Fukaya, Yuki; Takanashi, Koki*

no journal, , 

no abstracts in English

Oral presentation

Positron annihilation spectroscopy as a probe for spintronics; Hope to the first principles calculation

Kawasuso, Atsuo; Maekawa, Masaki; Fukaya, Yuki; Sakuraba, Yuya*; Saito, Eiji; Takanashi, Koki*

no journal, , 

Spin-polarized positron annihilation spectroscopy can be used for the studies of ferromagnetic electron momentum distribution and topmost surface electron spins. From this viewpoint, we argue the possibility of spin-polarized positron annihilation spectroscopy as a probe for spintronics materials. In the presentation, we introduce the theoretical formulation of the spin-polarized positron annihilation spectroscopy with some examples on classical ferromagnets, the latest results on the current-induced spin polarization, and some hopes to the first principles calculation to assist experiments.

Oral presentation

Observation of spin-polarized Weyl cones and giant anomalous Nernst effect in Co$$_2$$MnGa films

Sumida, Kazuki; Sakuraba, Yuya*; Masuda, Keisuke*; Kono, Takashi*; Kakoki, Masaaki*; Goto, Kazuki*; Zhou, W.*; Miyamoto, Koji*; Miura, Yoshio*; Okuda, Taichi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Observation of spin-polarized Weyl cones and giant anomalous Nernst effect in ferromagnetic Co$$_2$$MnGa films

Sumida, Kazuki; Sakuraba, Yuya*; Masuda, Keisuke*; Kono, Takashi*; Kakoki, Masaaki*; Goto, Kazuki*; Zhou, W.*; Miyamoto, Koji*; Miura, Yoshio*; Okuda, Taichi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Spin-polarized Weyl cones and giant anomalous Nernst effect in Co$$_2$$MnGa films

Sumida, Kazuki; Sakuraba, Yuya*; Masuda, Keisuke*; Kono, Takashi*; Kakoki, Masaaki*; Goto, Kazuki*; Zhou, W.*; Miyamoto, Koji*; Miura, Yoshio*; Okuda, Taichi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Observation of temperature dependence of spin-polarized electronic structure in Co$$_2$$MnSi Heusler alloy films

Sumida, Kazuki; Kakoki, Masaaki*; Sakuraba, Yuya*; Masuda, Keisuke*; Kono, Takashi*; Goto, Kazuki*; Miyamoto, Koji*; Miura, Yoshio*; Hono, Kazuhiro*; Okuda, Taiichi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Observation of spin-polarized Weyl cones and half-metallicity in the quaternary Heusler Co$$_2$$Mn(Al,Si) thin films

Sumida, Kazuki; Kakoki, Masaaki*; Sakuraba, Yuya*; Kono, Takashi*; Goto, Kazuki*; Miyamoto, Koji*; Hono, Kazuhiro*; Okuda, Taichi*; Kimura, Akio*

no journal, , 

no abstracts in English

Oral presentation

Temperature-dependent spin-polarized electronic structure of the half-metallic Heusler alloy Co$$_2$$MnSi films

Sumida, Kazuki; Kakoki, Masaaki*; Sakuraba, Yuya*; Masuda, Keisuke*; Kono, Takashi*; Goto, Kazuki*; Miyamoto, Koji*; Miura, Yoshio*; Hono, Kazuhiro*; Okuda, Taichi*; et al.

no journal, , 

17 (Records 1-17 displayed on this page)
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