Change in magnetic properties induced by swift heavy ion irradiation in CeO

Shimizu, Hirotaka*; Kosugi, Shinya*; Tahara, Yuki*; Yasunaga, Kazufumi*; Kaneta, Yasunori*; Ishikawa, Norito; Hori, Fuminobu*; Matsui, Toshiyuki*; Iwase, Akihiro*

Nuclear Instruments and Methods in Physics Research B, 286, p.291 - 294, 2012/09

https://doi.org/10.1016/j.nimb.2012.01.008

We have studied the magnetic properties of pure CeO irradiated with swift heavy ions. Experiment a results showed that the ferromagnetism was induced even at room temperature by 200 MeV Xe ion irradiation. The value of saturation magnetization, Ms, systematically changes as a function of ion-fluence. The X-ray diffraction (XRD) spectra show that the lattice constant of CeO increases with increasing ion-fluence. This result and our previous XPS result show that the ion-irradiation produced oxygen vacancies. The present study implies that the ferromagnetic behavior of the ion-irradiated CeO is attributed to the magnetic moments of localized 4f electrons on Ce atoms, which are related to oxygen vacancies.

X-ray study of radiation damage in UO irradiated with high-energy heavy ions

Ishikawa, Norito; Sonoda, Takeshi*; Okamoto, Yoshihiro; Sawabe, Takashi*; Takegahara, Keisuke; Kosugi, Shinya*; Iwase, Akihiro*

Journal of Nuclear Materials, 419(1-3), p.392 - 396, 2011/12

https://doi.org/10.1016/j.jnucmat.2011.08.013

In order to characterize the radiation damage due to ion-track formation in UO, polycrystalline samples have been irradiated with 210-MeV Xe ions, and measured with XRD (X-ray diffraction) technique using Cu X-ray. We have also tried EXAFS (extended X-ray absorption fine structure) measurement using X-ray near U L-edge. The results show that XRD technique detects damage at relatively low fluence of 10 ions/m and higher, while the irradiation-induced change of EXAFS spectra is not observed even at highest fluence of 10 ions/m. The damage detection may be critically influenced by the depth profile of X-ray penetration.

Effect of high temperature annealing on ferromagnetism induced by energetic ion irradiation in FeRh alloy

Kosugi, Shinya*; Fujita, Naoki*; Matsui, Toshiyuki*; Hori, Fuminobu*; Saito, Yuichi; Ishikawa, Norito; Okamoto, Yoshihiro; Iwase, Akihiro*

Nuclear Instruments and Methods in Physics Research B, 269(9), p.869 - 872, 2011/05

https://doi.org/10.1016/j.nimb.2010.12.061

Effects of thermal annealing on ion-irradiation induced ferromagnetism of FeRh bulk alloy and the related structural change were investigated by means of superconducting quantum interference device (SQUID) and extended X-ray absorption fine structure (EXAFS), respectively. Depending on the annealing temperature from 100 to 500 C, the magnetization induced by 10 MeV iodine ion irradiation and the lattice structure of the alloy were remarkably changed. After 500 C annealing, the magnetization and the lattice ordering of the alloy become similar to the states before the irradiation. The experimental result indicates that the thermal relaxation of irradiation-induced atomic disordering dominates the magnetic state of ion-irradiated FeRh alloy.

Determination of threshold energies for displacements of Fe and Rh atoms in Fe-50 at.%Rh intermetallic compound by using energetic electron irradiation at low temperatures

Kosugi, Shinya*; Ishikawa, Norito; Saito, Yuichi; Hori, Fuminobu*; Iwase, Akihiro*

Journal of Nuclear Materials, 411(1-3), p.171 - 173, 2011/04

https://doi.org/10.1016/j.jnucmat.2011.01.116

Changes in electrical resistivity induced by irradiation with energetic electrons were measured for Fe-50 at.%Rh alloy as a function of electron energy in the range from 0.5 to 2.0 MeV. The irradiation was carried out below 20 K and the resistivity was measured at 10 K. The electron energy dependence of the resistivity change rate was analysed by using a simple displacement theory, and the average threshold energies for atomic displacements, , were determined as 30 eV for Fe and 45 eV for Rh.

Micrometer-sized magnetic patterning of FeRh films using an energetic ion microbeam

Fujita, Naoki*; Matsui, Toshiyuki*; Kosugi, Shinya*; Sato, Takahiro; Saito, Yuichi; Takano, Katsuyoshi; Koka, Masashi; Kamiya, Tomihiro; Seki, Shu*; Iwase, Akihiro*

Japanese Journal of Applied Physics, 49(6), p.060211_1 - 060211_3, 2010/06

https://doi.org/10.1143/JJAP.49.060211

Study on effects of swift heavy ion irradiation on the crystal structure in CeO doped with GdO

Tahara, Yuki*; Zhu, B.-L.*; Kosugi, Shinya*; Ishikawa, Norito; Okamoto, Yoshihiro; Baba, Yuji; Hirao, Norie; Hori, Fuminobu*; Matsui, Toshiyuki*; Iwase, Akihiro*

no journal, , 

In present light-water nuclear power plants, it is useful to dope some elements, which have a high neutron absorption cross section, into fuels (UO) in order to control the initial reactivity. During the operation of reactors, UO fuels are exposed to irradiation with high energy fission products which have energies around 100 MeV. Therefore, it is important to study the effects of high energy fission products on UO fuels. Cerium dioxide (CeO) has been used so far as a simulation material for UO because it has the same fluorite structure as that of UO. In this study, CeO pellets doped with GdO were irradiated with 200 MeV Xe ions to simulate the irradiation effects of high energy fission products on UO doped with GdO. The X-ray diffraction spectra show that the lattice constant of CeO increases with increasing the amount of the Gd-doping. In addition, it also increases by the irradiation and the effect of the irradiation becomes more remarkable by doping GdO.

Raddiation effect of swift heavy ions on the structure of CeO doped with GdO and ErO

Tahara, Yuki*; Zhu, B.-L.*; Kosugi, Shinya*; Hori, Fuminobu*; Matsui, Toshiyuki*; Iwase, Akihiro*; Ishikawa, Norito; Okamoto, Yoshihiro; Baba, Yuji; Hirao, Norie

no journal, , 

no abstracts in English