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Journal Articles

Effect of cotunneling and spin polarization on the large tunneling magnetoresistance effect in granular C$$_{60}$$-Co films

Sakai, Seiji; Mitani, Seiji*; Sugai, Isamu; Takanashi, Koki; Matsumoto, Yoshihiro; Entani, Shiro; Naramoto, Hiroshi*; Avramov, P.; Maeda, Yoshihito

Physical Review B, 83(17), p.174422_1 - 174422_6, 2011/05

 Times Cited Count:8 Percentile:39.13(Materials Science, Multidisciplinary)

Journal Articles

Surface-assisted spin Hall effect in Au films with Pt impurities

Gu, B.; Sugai, Isamu*; Ziman, T.*; Guo, G. Y.*; Nagaosa, Naoto; Seki, Takeshi*; Takanashi, Koki; Maekawa, Sadamichi

Physical Review Letters, 105(21), p.216401_1 - 216401_4, 2010/11

 Times Cited Count:63 Percentile:90.42(Physics, Multidisciplinary)

Journal Articles

Composition dependence of magnetic and magnetotransport properties in C$$_{60}$$-Co granular thin films

Sugai, Isamu*; Sakai, Seiji; Matsumoto, Yoshihiro; Naramoto, Hiroshi*; Mitani, Seiji*; Takanashi, Koki; Maeda, Yoshihito

Journal of Applied Physics, 108(6), p.063920_1 - 063920_7, 2010/09

 Times Cited Count:8 Percentile:36.82(Physics, Applied)

Journal Articles

The Electronic structures of fullerene/transition-metal hybrid material

Matsumoto, Yoshihiro; Sakai, Seiji; Naramoto, Hiroshi*; Hirao, Norie*; Baba, Yuji; Shimada, Toshihiro*; Sugai, Isamu; Takanashi, Koki; Maeda, Yoshihito

Materials Research Society Symposium Proceedings, Vol.1081 (Internet), 6 Pages, 2008/03

Recently, we have found the appearance of substantial MR ratio (80%) in a C$$_{60}$$/Co hybrid material. Such the MR ratio cannot be explained enough only by tunnel conduction through Co grains. Therefore, to obtain information about electronic structures of C$$_{60}$$/Co hybrid material is necessary. Absorption spectra of C$$_{60}$$Co are different from that of pristine C$$_{60}$$. In particular, peak intensity corresponding to $$pi$$ $$^*$$(LUMO) $$leftarrow$$ C 1s excitation of C$$_{60}$$Co is clearly attenuated. In addition, C 1s photoelectron peak of C$$_{60}$$Co slightly shifted to lower binding energy compared to that of pristine C$$_{60}$$. These results indicate that 3d electron of Co transfers to $$pi$$ $$^*$$ orbital of C$$_{60}$$ and new electronic states are formed in the C$$_{60}$$-Co compound. In fact, XPS spectra of valence excitation region also demonstrate the formation of hybrid orbital near the Fermi level due to the coupling of C$$_{60}$$ and Co.

Journal Articles

Giant tunnel magnetoresistance in codeposited fullerene-cobalt films in the low bias-voltage regime

Sakai, Seiji; Sugai, Isamu; Mitani, Seiji*; Takanashi, Koki; Matsumoto, Yoshihiro; Naramoto, Hiroshi*; Avramov, P.; Okayasu, Satoru; Maeda, Yoshihito

Applied Physics Letters, 91(24), p.242104_1 - 242104_3, 2007/12

 Times Cited Count:30 Percentile:73.93(Physics, Applied)

Journal Articles

Magnetic and magnetotransport properties in nanogranular Co/C$$_{60}$$-Co film with high magnetoresistance

Sakai, Seiji; Yakushiji, Kei*; Mitani, Seiji*; Sugai, Isamu; Takanashi, Koki*; Naramoto, Hiroshi*; Avramov, P.; Lavrentiev, V.*; Narumi, Kazumasa; Maeda, Yoshihito

Materials Transactions, 48(4), p.754 - 758, 2007/04

 Times Cited Count:8 Percentile:51.29(Materials Science, Multidisciplinary)

Magnetic properties were investigated for the alternately deposited film of C$$_{60}$$ and Co which has found to exhibit tunnel magnetoresistance (MR) of 10-80 %. Magnetic field and temperature dependences of magnetization showed typical superparamagnetic behaviors with the blocking temperature of 40 K. The magnetization curve at 300 K was well fitted by the Langevin function with the size distribution of Co particles, and the mean diameter and size distribution were evaluated to be 3.1 nm and 1 nm, respectively. Based on the magnetic properties, the detailed structure and magnetotransport properties are discussed.

Oral presentation

Tunnel magnetoresistance in granular Co-C$$_{60}$$ hybrid films

Sakai, Seiji; Sugai, Isamu; Yakushiji, Kei*; Mitani, Seiji*; Takanashi, Koki*; Naramoto, Hiroshi; Avramov, P.; Narumi, Kazumasa; Maeda, Yoshihito

no journal, , 

no abstracts in English

Oral presentation

Tunneling magnetotransport in hybrid system of cobalt and C$$_{60}$$

Sakai, Seiji; Sugai, Isamu; Yakushiji, Kei*; Mitani, Seiji*; Takanashi, Koki*; Naramoto, Hiroshi; Avramov, P.; Narumi, Kazumasa; Maeda, Yoshihito

no journal, , 

We have revealed that the Co/Co-C$$_{60}$$ films prepared by alt-deposition show the tunnel MR of a few 10% under low bias voltage and the further enhancement to above 80% by the voltage increase at lower temperature than 10 K. In the present study, the magnetotransport properties in the co-deposited Co/Co-C$$_{60}$$ films are reported. The co-deposited film shows the remarkable tunnel MR effect (10-50%) whose ratio is significantly influenced by the applied voltage. Such a significant MR enhancement by the bias-voltage is found to take place commonly in the Co/Co-C$$_{60}$$ films irrespective of the deposition method, and that is in contrast to the small extent of changes in the conventional metal/insulator systems. In the presentation, the comparative results for the co-deposited and alt-deposited Co/Co-C$$_{60}$$ films are also reported in comparison with the analyzed structures by Raman spectroscopy et al..

Oral presentation

Tunnel magnetoresistance effect in nano-granular Co/C60-Co films

Sakai, Seiji; Sugai, Isamu*; Mitani, Seiji*; Takanashi, Koki*; Naramoto, Hiroshi*; Avramov, P.; Okayasu, Satoru; Narumi, Kazumasa; Maeda, Yoshihito

no journal, , 

no abstracts in English

Oral presentation

Magnetoresistance and structure in C60-Co thin films

Sakai, Seiji; Sugai, Isamu; Mitani, Seiji*; Matsumoto, Yoshihiro; Takanashi, Koki; Naramoto, Hiroshi*; Okayasu, Satoru; Maeda, Yoshihito

no journal, , 

no abstracts in English

Oral presentation

Composition dependence of magnetic and magnetotransport properties in nanogranular C60-Co films

Sugai, Isamu; Sakai, Seiji; Mitani, Seiji*; Matsumoto, Yoshihiro; Takanashi, Koki; Naramoto, Hiroshi*; Avramov, P.; Okayasu, Satoru; Maeda, Yoshihito

no journal, , 

no abstracts in English

Oral presentation

Large tunnel magnetoresistance in Co-evaporated C60-Co thin films

Sakai, Seiji; Sugai, Isamu; Mitani, Seiji*; Matsumoto, Yoshihiro; Takanashi, Koki; Naramoto, Hiroshi*; Avramov, P.; Okayasu, Satoru; Maeda, Yoshihito

no journal, , 

Oral presentation

Composition dependence of tunnel magnetoresistance in C60-Co thin films

Sakai, Seiji; Sugai, Isamu; Matsumoto, Yoshihiro; Mitani, Seiji*; Takanashi, Koki; Naramoto, Hiroshi*; Avramov, P.; Okayasu, Satoru; Maeda, Yoshihito

no journal, , 

no abstracts in English

Oral presentation

Giant TMR effect and spin states of C$$_{60}$$-Co thin films

Sakai, Seiji; Matsumoto, Yoshihiro; Sugai, Isamu*; Mitani, Seiji*; Takanashi, Koki; Takagi, Yasumasa*; Nakagawa, Takeshi*; Yokoyama, Toshihiko*; Shimada, Toshihiro*; Maeda, Yoshihito

no journal, , 

no abstracts in English

Oral presentation

Electronic and spin states and giant tunnel magnetoresistance effect in C$$_{60}$$-Co hybrid films

Sakai, Seiji; Matsumoto, Yoshihiro; Sugai, Isamu*; Mitani, Seiji*; Takanashi, Koki; Takagi, Yasumasa*; Nakagawa, Takeshi*; Yokoyama, Toshihiko*; Shimada, Toshihiro*; Naramoto, Hiroshi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Systematic study of magneto-transport properties of C$$_{60}$$-Co films with giant tunnel magnetoresistance

Sakai, Seiji; Matsumoto, Yoshihiro; Sugai, Isamu*; Mitani, Seiji*; Takanashi, Koki; Naramoto, Hiroshi*; Okayasu, Satoru; Maeda, Yoshihito

no journal, , 

no abstracts in English

Oral presentation

Giant TMR effect in Granular-structured C$$_{60}$$-Co hybrid films

Sakai, Seiji; Matsumoto, Yoshihiro; Sugai, Isamu*; Mitani, Seiji*; Takanashi, Koki; Takagi, Yasumasa*; Nakagawa, Takeshi*; Yokoyama, Toshihiko*; Naramoto, Hiroshi*; Maeda, Yoshihito

no journal, , 

In the present study, the V and T dependences of the TMR effect are investigated intensively for the co-deposited C$$_{60}$$-Co films with different compositions. The mechanism of the giant TMR effect is discussed taking our recent results for the microstructures of the granular films (i.e., a hybrid structure of the covalent C$$_{60}$$-Co compound and Co nanoparticles dispersed therein) and the electronic and spin states of the C$$_{60}$$-Co compound studied by XPS and X-ray magnetic circular dichroism (XMCD) spectroscopy into account.

Oral presentation

Magnetotransport properties of C$$_{60}$$-Co thin films with current-perpendicular-to-plane devise structures

Sakai, Seiji; Matsumoto, Yoshihiro; Sugai, Isamu*; Mitani, Seiji*; Takanashi, Koki; Maeda, Yoshihito

no journal, , 

no abstracts in English

Oral presentation

Effect of highly spin-polarized interfaces on giant tunnel magnetoresistance in granular structured C60-Co films

Sakai, Seiji; Matsumoto, Yoshihiro; Entani, Shiro; Sugai, Isamu*; Mitani, Seiji*; Takanashi, Koki; Naramoto, Hiroshi*; Maeda, Yoshihito

no journal, , 

no abstracts in English

Oral presentation

Analysis of giant tunnel magnetoresistance effect in granular C60-Co films

Sakai, Seiji; Matsumoto, Yoshihiro; Entani, Shiro; Sugai, Isamu*; Mitani, Seiji*; Takanashi, Koki; Naramoto, Hiroshi*; Maeda, Yoshihito

no journal, , 

no abstracts in English

27 (Records 1-20 displayed on this page)