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Journal Articles

New material exploration to enhance neutron intensity below cold neutrons; Nanosized graphene flower aggregation

Teshigawara, Makoto; Ikeda, Yujiro*; Yan, M.*; Muramatsu, Kazuo*; Sutani, Koichi*; Fukuzumi, Masafumi*; Noda, Yohei*; Koizumi, Satoshi*; Saruta, Koichi; Otake, Yoshie*

Nanomaterials (Internet), 13(1), p.76_1 - 76_9, 2023/01

 Times Cited Count:0 Percentile:59.51(Chemistry, Multidisciplinary)

To enhance neutron intensity below cold neutrons, it is proposed that nanosized graphene aggregation could facilitate neutron coherent scattering under particle size conditions similar to nanodiamond. It might also be possible to use it in high neutron radiation conditions due to graphene's strong sp2 bonds. Using the RIKEN accelerator-driven compact neutron source and iMATERIA at J-PARC, we performed neutron measurement experiments, total neutron cross-section, and small-angle neutron scattering on nanosized graphene aggregation. The measured data revealed, for the first time, that nanosized graphene aggregation increased the total cross-sections and small-angle scattering in the cold neutron energy region, most likely due to coherent scattering, resulting in higher neutron intensities, similar to nanodiamond.

Journal Articles

Characterization of swift heavy ion-induced defects in Fe-Rh alloy by using positron beam technique

Hori, Fuminobu*; Fukuzumi, Masafumi*; Kawasuso, Atsuo; Zushi, Yoshihiro*; Chimi, Yasuhiro; Ishikawa, Norito; Iwase, Akihiro*

Physica Status Solidi (C), 4(10), p.3530 - 3533, 2007/09

 Times Cited Count:0 Percentile:0.07

no abstracts in English

Journal Articles

Ion-species dependence of swift heavy ion-induced ferromagnetism of Fe-50at.%Rh alloy at low temperatures

Zushi, Yoshihiro*; Fukuzumi, Masafumi*; Chimi, Yasuhiro; Ishikawa, Norito; Ono, Fumihisa*; Iwase, Akihiro*

Nuclear Instruments and Methods in Physics Research B, 256(1), p.434 - 437, 2007/03

 Times Cited Count:23 Percentile:81.85(Instruments & Instrumentation)

Fe-50at.%Rh alloys were irradiated with swift heavy ions such as 120 MeV Ni, 150 MeV Kr, 200 MeV Xe, 200 MeV Au, and it is found that low-temperature antiferromagnetic state changes to ferromagnetic state after the irradiations. The ion-fluence dependence and ion-species dependence was investigated. It is found that saturated magnetization evolves as fluence increases, and the evolution behavior for different ion-species differs from each other, but it scales with single universal curve as a function of total energy deposition via elastic collision.

Journal Articles

Study on irradiation-induced magnetic transition in FeRh alloys by means of Fe K-edge XMCD spectroscopy

Iwase, Akihiro*; Fukuzumi, Masafumi*; Zushi, Yoshihiro*; Suzuki, Motohiro*; Takagaki, Masafumi*; Kawamura, Naomi*; Chimi, Yasuhiro; Mizuki, Junichiro; Ishikawa, Norito; Ono, Fumihisa*

Nuclear Instruments and Methods in Physics Research B, 256(1), p.429 - 433, 2007/01

 Times Cited Count:17 Percentile:73.84(Instruments & Instrumentation)

We have studied the effects of swift heavy ion irradiation on the magnetic properties of Fe-Rh intermetallic compound by using Fe K-edge X-ray magnetic circular dichroism (XMCD) at 20 K. For an unirrdaiated specimen, no signal of XMCD spectrum has been observed because Fe-Rh intermetallic compound is intrinsically anti-ferromagnetic below room temperature. For the specimens irradiated with 120-200 MeV Ni, Kr, Xe or Au ions, we have found XMCD spectra which are characterized by a dispersion-type profile with a positive peak and a negative peak near Fe K-edge. The intensity of XMCD spectra remarkably depends on ion-fluence and ion-mass. The experimental result implies that the ferromagnetic state is induced by the swift heavy ion irradiation. The change in magnetic state of Fe element is discussed in terms of energy deposition through the elastic and electronic processes.

Journal Articles

Effects of swift heavy ion irradiation on magnetic properties of Fe-Rh alloy

Fukuzumi, Masafumi*; Chimi, Yasuhiro; Ishikawa, Norito; Suzuki, Motohiro*; Takagaki, Masafumi*; Mizuki, Junichiro; Ono, Fumihisa*; Neumann, R.*; Iwase, Akihiro*

Nuclear Instruments and Methods in Physics Research B, 245(1), p.161 - 165, 2006/04

 Times Cited Count:17 Percentile:74.73(Instruments & Instrumentation)

We have performed swift heavy ion irradiations in Fe-50at.%Rh alloys at room temperature. Before and after the irradiations, the magnetic properties and the lattice structure are measured using Superconducting QUantum Interference Device (SQUID) and X-Ray Diffractometer (XRD), respectively. We have also performed X-ray Magnetic Circular Dichroism (XMCD) measurement near the Fe K-edge at the synchrotron radiation facility, SPring-8, to examine the irradiation-induced ferromagnetic state near the specimen surface. We have found that the swift heavy ion irradiations induce the ferromagnetic state in Fe-50at.%Rh alloy below the antiferromagnetism-ferromagnetism transition temperature of the unirradiated alloy and the lattice expasion by 0.3%. For the specimens irradiated with swift heavy ions, we observe the XMCD spectra correponding to ferromagnetisim, which depend on the mass of irradiating ions and/or irradiation fluence. Effects of energy loss through electronic excitation and elastic collisions on lattice and magnetic structures of Fe-Rh alloy are discussed.

Journal Articles

Observation of ion-irradiation induced diffusion in Pd-Si system using synchrotron radiation X-ray photoelectron spectroscopy

Iwase, Akihiro*; Chimi, Yasuhiro; Ishikawa, Norito; Nakatani, Rikizo*; Kato, Yuzaburo*; Fukuzumi, Masafumi*; Tsuchida, Hidetsugu*; Baba, Yuji

Nuclear Instruments and Methods in Physics Research B, 245(1), p.141 - 144, 2006/04

 Times Cited Count:0 Percentile:0.01(Instruments & Instrumentation)

Diffusion of Si atoms in Pd under energetic ion irradiation is studied in Pd-Si thin layer system using synchrotron radiation photoemission spectroscopy. Specimens are prepared by depositing Pd on Si single crystals. The Pd layer thicknesses are 10-300 nm. Before irradiation, we observe photoemission spectra only for Pd, but do not find any trace of Si. After irradiation with 3-MeV Si ions, 1-MeV O ions or 200-MeV Xe ions, we observe an additional photoemission component at the binding energy about 3 eV higher than that of Si 1s bulk component. The experimental result implies that the energetic ion-irradiation induces the diffusion of Si atoms from the Si-Pd interface to the Pd layer surface. The shift of the binding energy from the value for the Si bulk can be interpreted as arising from electron charge transfer from Si to Pd. The dependences of photoemission spectra and ion-irradiation induced diffusion on ion-species and ion-fluence are discussed.

Oral presentation

Effects of carbon cluster ion irradiation in oxides

Ishikawa, Norito; Chimi, Yasuhiro; Michikami, Osamu*; Ota, Yasuyuki*; Saito, Yuichi; Chiba, Atsuya; Fukuzumi, Masafumi*; Hori, Fuminobu*; Iwase, Akihiro*

no journal, , 

no abstracts in English

Oral presentation

Positron annihilation study of radiation induced magnetic transformation in FeRh alloy

Hori, Fuminobu*; Fukuzumi, Masafumi*; Kawasuso, Atsuo; Iwase, Akihiro*

no journal, , 

no abstracts in English

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