JOPSS - Search Results

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 (LUMO) 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 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：70.87(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：52.62(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

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

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

no journal, ,

We investigated the bias-voltage (V) and temperature (T) dependences of the spin-dependent transport properties of the granular C60-Co films in the current perpendicular to plane (CPP) geometry. At low T, each sample shows 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 (T=2K), which changes depending on the sample composition and device structure. By considering this enhancement effect, we can estimate the spin-polarization at the C60-Co compound/Co interface. The estimated values are remarkably high, i.e., P=75% at zero temperature, compared to Co crystal(P=30%), and almost independent of the samples. The detailed results on the transport properties and X-ray magnetic circular dichroism spectroscopy were presented in the conference.

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

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

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

The Electronic structures of fullerene/transition-metal hybrid material

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

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

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

Fullerene-cobalt hybrid system with large spin polarization

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

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

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

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

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

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

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

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

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

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

Giant TMR effect and interface spin-polarization of C60-Co films

Giant tunnel magnetoresistance and interface spin-polarization in granular C60-Co films