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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

https://doi.org/10.1103/PhysRevB.83.174422
 Times Cited Count：8 Percentile：33.85(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

https://doi.org/10.1103/PhysRevLett.105.216401
 Times Cited Count：72 Percentile：89.53(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

https://doi.org/10.1063/1.3471800
 Times Cited Count：8 Percentile：32.73(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

https://doi.org/10.1063/1.2822397
 Times Cited Count：30 Percentile：70.30(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

https://doi.org/10.2320/matertrans.48.754
 Times Cited Count：10 Percentile：51.85(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

Effect of highly spin-polarized interfaces on giant tunnel magnetoresistance in granular structured C$$_{60}$$-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

Oral presentation

Giant TMR effect and interface spin-polarization of 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

Highly spin-polarized tunnel magnetoresistance in granular C$$_{60}$$-Co films

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

no journal, , 

In the present study, we examine the bias-voltage (V) and temperature (T) dependences of the spin-dependent transport properties of the granular C$$_{60}$$-Co films (C$$_{60}$$Co$$_{6-10}$$) in the current perpendicular to plane (CPP) geometry for the origin of the large TMR effect. At low T, the CPP samples show much higher MR than the upper limit of TMR (MR = 50%) derived from the Julliere's model. From the I-V characteristics, we evaluated the degree of the higher order tunneling process, as a possible cause of the MR enhancement above MR = 50%, to be 3-7 at low temperatures, which changes depending on the sample composition and device structure. After considering this MR enhancement effect, we can evaluate the spin-polarization of the tunneling electrons generated at the C$$_{60}$$-Co compound/Co interface. The evaluated values are remarkably high, i.e., P $$>$$ 75% at zero temperature, compared to Co crystal (P = 30%).

Oral presentation

Spin-polarized current flow in the C$$_{60}$$-Co hybrid films with giant TMR effect

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

no journal, , 

no abstracts in English

Oral presentation

Higly spin-polarized current in C$$_{60}$$-Co films

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

no journal, , 

no abstracts in English

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

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

Composition dependence of tunnel magnetoresistance in C$$_{60}$$-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

Highly spin-polarized tunneling current in C$$_{60}$$-Co granular 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

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

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

27 (Records 1-20 displayed on this page)