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Journal Articles

R&D of digital technology on inverse estimation of radioactive source distributions and related source countermeasures; R&D status of digital platform including 3D-ADRES-indoor

Machida, Masahiko; Yamada, Susumu; Kim, M.; Okumura, Masahiko; Miyamura, Hiroko; Shikaze, Yoshiaki; Sato, Tomoki*; Numata, Yoshiaki*; Tobita, Yasuhiro*; Yamaguchi, Takashi; et al.

RIST News, (69), p.2 - 18, 2023/09

The contamination of radioactive materials leaked from the reactor has resulted in numerous hot spots in the Fukushima Daiichi Nuclear Power Station (1F) building, posing obstacles to its decommissioning. In order to solve this problem, JAEA has conducted research and development of the digital technique for inverse estimation of radiation source distribution and countermeasures against the estimated source in virtual space for two years from 2021 based on the subsidy program "Project of Decommissioning and Contaminated Water Management" performed by the funds from the Ministry of Economy, Trade and Industry. In this article, we introduce the results of the project and the plan of the renewal project started in April 2023. For the former project, we report the derivative method for LASSO method considering the complex structure inside the building and the character of the source and show the result of the inverse estimation using the method in the real reactor building. Moreover, we explain the platform software "3D-ADRES-Indoor" which integrates these achievements. Finally, we introduce the plan of the latter project.

Journal Articles

Outlining zircon growth in a granitic pluton using 3D cathodoluminescence patterns, U-Pb age, titanium concentration, and Th/U; Implications for the magma chamber process of Okueyama granite, Kyushu, Japan

Yuguchi, Takashi*; Ito, Daichi*; Yokoyama, Tatsunori; Sakata, Shuhei*; Suzuki, Satoshi*; Ogita, Yasuhiro; Yagi, Koshi*; Imura, Takumi*; Motai, Satoko*; Ono, Takeshi*

Lithos, 440-441, p.107026_1 - 107026_14, 2023/03

 Times Cited Count:0 Percentile:0.02(Geochemistry & Geophysics)

We propose a new method for elucidating zircon growth in granitic plutons, based on variations in three-dimensional 3D cathodoluminescence (CL) patterns, U-Pb ages, titanium concentration, and Th/U ratios. We focused on the zircon growth processes in the Okueyama granite (OKG) in central Kyushu, Japan, to obtain interpretations of magma chamber processes that result in the formation of granitic plutons. The OKG consists of three lithofacies: biotite granite (BG), hornblende granite (HG), and hornblende granodiorite (HGD). To determine the 3D internal structure and growth pattern of a zircon crystal, we performed CL observations for multi-sections of the samples. Simultaneously, we also determined the zircon U-Pb age and titanium concentration of the center sections of the samples. The 3D distribution of the oscillatory zoning can be used to determine the crystal nucleus. The simultaneous determination of zircon U-Pb ages and Ti concentrations of the granite samples indicates the time-temperature (t-T) history of granitic magma before its solidification. The t-T histories of the BG, HG, and HGD represented similar cooling behaviors within the magma chamber: rapid cooling from the zircon crystallization temperature to the closure temperature of the biotite K-Ar system between 16 Ma and 10 Ma. The variations in the Th/U ratios against temperature also demonstrate a different trend at the boundary of approximately 670 $$^{circ}$$C. Fractional crystallization in the magma chamber progressed significantly at temperatures above 670 $$^{circ}$$C; below 670 $$^{circ}$$C, crystallization progressed slowly, indicating only minimal changes in the magma composition. The variations in the Th/U ratio against temperature in the BG, HG, and HGD portrayed common tendencies, indicating the same behavior in the progression of fractional crystallization among the three lithofacies, which in turn, represented the same behavior within the entire magma chamber.

Journal Articles

Simultaneous determination of zircon crystallisation age and temperature; Common thermal evolution of mafic magmatic enclaves and host granites in the Kurobegawa granite, central Japan

Yuguchi, Takashi*; Yamazaki, Hayato*; Ishibashi, Kozue*; Sakata, Shuhei*; Yokoyama, Tatsunori; Suzuki, Satoshi*; Ogita, Yasuhiro; Sando, Kazusa*; Imura, Takumi*; Ono, Takeshi*

Journal of Asian Earth Sciences, 226, p.105075_1 - 105075_9, 2022/04

 Times Cited Count:3 Percentile:52.46(Geosciences, Multidisciplinary)

Simultaneous determination of the U-Pb age of zircon and concentration of titanium in a single analysis spot, using inductively coupled plasma mass spectrometry with laser ablation sample introduction, produces paired age and temperature data of zircon crystallisation, potentially revealing time-temperature ($$t-T$$) histories for evolved magma. The Kurobegawa granite, central Japan, contains abundant mafic magmatic enclaves (MMEs). We applied this method to evaluate MMEs and their host (enclosing) granites. Cooling behaviour common to both MMEs and host rocks was found between 1.5 and 0.5 Ma. Rapid cooling from the zircon crystallisation temperature to the closure temperature of biotite K-Ar system was within $$sim$$1 million year. Combining the obtained $$t-T$$ paths of MMEs and host rocks with petrological information can provide insights into magma chamber processes. This suggests that MME flotation, migration, and spread through the magma chamber ceased at 1.5-0.5 Ma, indicating the emplacement age of the Kurobegawa granitic pluton, as no large-scale reheating episodes have occurred since then.

Journal Articles

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

 Times Cited Count:30 Percentile:96.87(Astronomy & Astrophysics)

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 $$^{circ}$$C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 $$^{circ}$$C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.

Journal Articles

JAEA activities related to the use of computer programs and databases in the nuclear field

Suzuki, Yoshio; Otani, Takayuki; Sakamoto, Kensaku; Takakura, Masahiro*; Kuwabara, Yasuhiro*

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.287 - 294, 2020/10

HPC Technology Promotion Office, Center for Computational Science and e-systems (CCSE) of Japan Atomic Energy Agency (JAEA) is responsible for the administration of computer programs (CPs) and databases (DBs) developed in JAEA to disseminate R&D results in JAEA to the outside and improve R&D efficiency. The information of these CPs and DBs can be found using Program and Database retrieval System (PRODAS) (https://prodas.jaea.go.jp), which is developed by our team. Those in Japan can also obtain CPs and DBs in the nuclear field possessed in OECD NEA Data Bank (NEADB), Radiation Safety Information Computational Center (RSICC) in the United States, and International Atomic Energy Agency (IAEA). In this paper, the recent situation of possession and dispatch of CPs and DBs developed within JAEA and the frameworks to obtain and provide CPs and DBs in nuclear field worldwide are presented.

Journal Articles

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.

Science, 364(6437), p.272 - 275, 2019/04

 Times Cited Count:233 Percentile:99.74(Multidisciplinary Sciences)

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

Journal Articles

The Study of the magnetization process of Fe film by magnetic Compton scattering and M$"o$ssbauer spectroscopy

Agui, Akane; Masuda, Ryo*; Kobayashi, Yasuhiro*; Kato, Tadashi*; Emoto, Shun*; Suzuki, Kosuke*; Sakurai, Hiroshi*

Journal of Magnetism and Magnetic Materials, 408, p.41 - 45, 2016/06

AA2015-0849.pdf:1.54MB

 Times Cited Count:4 Percentile:21.44(Materials Science, Multidisciplinary)

We investigated the magnetization process of Fe (110) film using the field dependence of magnetic Compton scattering and M$"o$ssbauer spectroscopy. From the magnetic Compton profiles, the spin and orbital magnetic moment specific magnetization versus magnetizing field curves were obtained. From the M$"o$ssbauer spectra, the angles between the magnetizing field and the magnetic moment were obtained. It was found that the magnetizing field dependence of the ratio between orbital moment and spin moment was related to the angles between the magnetizing field and the magnetic moment. We indicate that the magnetic field dependence of the orbital magnetic moment plays a role in the magnetization process.

Journal Articles

X-ray absorption spectroscopy in the heavy Fermion compound $$alpha$$-YbAlB$$_4$$ at high magnetic fields

Terashima, Taku*; Matsuda, Yasuhiro*; Kuga, Kentaro*; Suzuki, Shintaro*; Matsumoto, Yosuke*; Nakatsuji, Satoru*; Kondo, Akihiro*; Kindo, Koichi*; Kawamura, Naomi*; Mizumaki, Masaichiro*; et al.

Journal of the Physical Society of Japan, 84(11), p.114715_1 - 114715_4, 2015/11

 Times Cited Count:4 Percentile:35.01(Physics, Multidisciplinary)

Journal Articles

Development of an unstable failure analysis procedure considering change of compliance at a crack part of SFR pipes

Wakai, Takashi; Machida, Hideo*; Yoshida, Shinji*; Yanagihara, Seiji*; Suzuki, Ryosuke*; Matsubara, Masaaki*; Enuma, Yasuhiro

Engineering Failure Analysis, 56, p.484 - 500, 2015/10

 Times Cited Count:1 Percentile:11.98(Engineering, Mechanical)

Journal Articles

Synchrotron X-ray spectroscopy study on the valence state and magnetization in $$alpha$$-YbAl$$_{1-x}$$Fe$$_x$$B$$_4$$ ($$x=0.115$$) at low temperatures and high magnetic fields

Terashima, Taku*; Matsuda, Yasuhiro*; Kuga, Kentaro*; Suzuki, Shintaro*; Matsumoto, Yosuke*; Nakatsuji, Satoru*; Kondo, Akihiro*; Kindo, Koichi*; Kawamura, Naomi*; Mizumaki, Masaichiro*; et al.

Journal of Physics; Conference Series, 592(1), p.012020_1 - 012020_6, 2015/03

 Times Cited Count:1 Percentile:43.31

Valence fluctuation phenomena in rare-earth intermetallic compounds have attracted attention because the quantum criticality of the valence transition has been proposed theoretically. Recently, it was found that $$beta$$-YbAlB$$_4$$ shows quantum criticality without tuning and has a strong mixed-valence state. In this study, we measured the magnetization curve and X-ray magnetoabsorption in $$alpha$$-YbAl$$_{1-x}$$Fe$$_x$$B$$_4$$ ($$x=0.115$$), which is a locally isostructural polymorph of $$beta$$-YbAlB$$_4$$. The magnetization and X-ray experiments were performed in fields up to 55 and 40 T, respectively. A small increase in the Yb valence was observed at fields where the magnetization curve exhibited a change in slope.

Journal Articles

Effects of irradiation induced Cu clustering on vickers hardness and electrical resistivity of Fe-Cu model alloys

Tobita, Toru; Nakagawa, Sho*; Takeuchi, Tomoaki; Suzuki, Masahide; Ishikawa, Norito; Chimi, Yasuhiro; Saito, Yuichi; Soneda, Naoki*; Nishida, Kenji*; Ishino, Shiori*; et al.

Journal of Nuclear Materials, 452(1-3), p.241 - 247, 2014/09

 Times Cited Count:15 Percentile:76.9(Materials Science, Multidisciplinary)

Three kinds of Fe-based model alloys, Fe-0.018 atomic percent (at.%) Cu, Fe-0.53at.%Cu, and Fe-1.06at.%Cu were irradiated with 2 MeV electrons up to the dose of 2$$times$$10$$^{-5}$$ dpa at 250$$^{circ}$$C. After the irradiation, the increase in Vickers hardness and the decrease in electrical resistivity were observed. The increase in hardness by electron irradiation is proportional to the product of the Cu contents and the square root of the electron dose. The decrease in electrical resistivity is proportional to the product of the square of Cu contents and the electron dose. Cu clustering in the materials with electron irradiation and thermal aging was observed by means of the three dimensional atom probes (3D-AP). The change in Vickers hardness and electrical resistivity is well correlated with the volume fraction of Cu clusters.

Journal Articles

High-magnetic-field X-ray absorption and magnetic circular dichroism spectroscopy in the mixed-valent compound YbAgCu$$_4$$

Nakamura, Toshiyuki*; Matsuda, Yasuhiro*; Her, J.-L.*; Kindo, Koichi*; Michimura, Shinji*; Inami, Toshiya; Mizumaki, Masaichiro*; Kawamura, Naomi*; Suzuki, Motohiro*; Chen, B.*; et al.

Journal of the Physical Society of Japan, 81(11), p.114702_1 - 114702_11, 2012/11

 Times Cited Count:11 Percentile:57.68(Physics, Multidisciplinary)

The X-ray absorption and magnetic circular dichroism (MCD) spectra at the Yb L$$_3$$ edge were measured in the mixed-valent heavy fermion compound YbAgCu$$_4$$ at high magnetic fields and low temperatures. The magnetic-field-temperature (H-T) phase boundary determined by the valence state is in very good agreement with that determined by the magnetization. It is clearly found that the metamagnetism of this compound is due to the field induced valence transition. A distinctive positive peak of the XMCD spectra appears in the vicinity of the white line of the absorption due to Yb$$^{3+}$$ state, while no feature is observed in the XMCD spectra corresponding to the Yb$$^{2+}$$ state. A small negative XMCD peak was observed at a lower energy and was attributed to the quadrupole trasition from theoretical calcuration, which explains its peculicar magnetic field dependence.

Journal Articles

Valence fluctuation in YbAgCu$$_4$$ at high Magnetic fields

Matsuda, Yasuhiro*; Nakamura, Toshiyuki*; Her, J.-L.*; Kindo, Koichi*; Michimura, Shinji*; Inami, Toshiya; Mizumaki, Masaichiro*; Kawamura, Naomi*; Suzuki, Motohiro*; Chen, B.*; et al.

Journal of the Physical Society of Japan, 81(1), p.015002_1 - 015002_2, 2012/01

 Times Cited Count:11 Percentile:57.68(Physics, Multidisciplinary)

The valence change of Yb ion in YbAgCu$$_4$$ was measured by means of X-ray absorption spectroscopy under high magnetic fields up to 35T. The valence state of Yb in YbAgCu$$_4$$ at 4.8K significantly increases at the metamagnetic transition. The saturation value of $$v$$ at 55T is evaluated as 2.97 using the relation $$Delta M/Delta v$$ at 35T. This value is in good agreement with $$v$$ for the related compound YbInCu$$_4$$ at high temperatures and the Yb valence in the localized high-field phase. We conclude that the metamagnetic transition in YbAgCu$$_4$$ arises from the valence transition, as theoretically predicted.

Journal Articles

Orbital magnetism in Cd$$_2$$Os$$_2$$O$$_7$$ studied by X-ray magnetic circular dichroism

Matsuda, Yasuhiro*; Her, J.-L.*; Michimura, Shinji*; Inami, Toshiya; Suzuki, Motohiro*; Kawamura, Naomi*; Mizumaki, Masaichiro*; Kindo, Koichi*; Yamaura, Junichi*; Hiroi, Zenji*

Physical Review B, 84(17), p.174431_1 - 174431_5, 2011/11

 Times Cited Count:25 Percentile:69.69(Materials Science, Multidisciplinary)

X-ray magnetic circular dichroism (XMCD) at the $$L$$$$_{2,3}$$-edge of Os has been investigated in the antiferromagneticphase of Cd$$_2$$Os$$_2$$O$$_7$$, which exhibits a metal-insulator transition around 227 K. According to the sum rule, the XMCD spectra at 10 and 37 T clearly show that the ratio between the orbital magnetic moment ($$m_{rm L}$$) and spinmagnetic moment ($$m_{rm S}$$) is $$m_{rm L}/m_{rm S} = 0.16 pm 0.02$$, and that $$m_{rm L}$$ and $$m_{rm S}$$ are coupled in parallel ($$m_{rm L}parallel m_{rm S}$$). These phenomena are unusual in that the expected ground state of Os$$^{5+}$$ (5$$d^3$$) is an orbital singlet in a cubic crystal field, and $$m_{rm L}$$and $$m_{rm S}$$ should be antiparallel for a less than half-filled system in accordance with Hund's third rule. It is likely that the spin-orbit coupling is important for explaining the observed orbital magnetism.

Journal Articles

XMCD spectroscopy on valence fluctuating and heavy fermion compounds in very high magnetic fields up to 40 T

Matsuda, Yasuhiro*; Her, J. L.*; Inami, Toshiya; Owada, Kenji; Ouyang, Z. W.*; Okada, Kyoko*; Nojiri, Hiroyuki*; Mitsuda, Akihiro*; Wada, Hirofumi*; Yoshimura, Kazuyoshi*; et al.

Journal of Physics; Conference Series, 190, p.012019_1 - 012019_6, 2009/11

 Times Cited Count:7 Percentile:85.24

Journal Articles

X-ray magnetic circular dichroism of a valence fluctuating state in Eu at high magnetic fields

Matsuda, Yasuhiro*; Ouyang, Z. W.*; Nojiri, Hiroyuki*; Inami, Toshiya; Owada, Kenji; Suzuki, Motohiro*; Kawamura, Naomi*; Mitsuda, Akihiro*; Wada, Hirofumi*

Physical Review Letters, 103(4), p.046402_1 - 046402_4, 2009/07

 Times Cited Count:53 Percentile:87.17(Physics, Multidisciplinary)

X-ray magnetic circular dichroism (XMCD) at the Eu L edge in two compounds exhibiting valence fluctuation, namely EuNi$$_2$$(Si$$_{0.18}$$Ge$$_{0.82}$$)$$_2$$ and EuNi$$_2$$P$$_2$$, has been investigated at high magnetic fields of up to 40T. A distinct XMCD peak corresponding to the trivalent state (Eu$$^{3+}$$), whose ground state is nonmagnetic (J = 0), was observed in addition to the main XMCD peak corresponding to the magnetic (J = 7/2) divalent state (Eu$$^{2+}$$). This result indicates that the 5$$d$$ electrons belonging to both valence states are magnetically polarized. It was also found that the ratio $$P$$$$_{5d}$$(3+)/$$P$$$$_{5d}$$(2+) between the polarization of 5$$d$$ electrons($$P$$$$_{5d}$$) in the Eu$$^{3+}$$ state and that of Eu$$^{2+}$$ depends on the material. The possible origin of the XMCD and an explanation of the material dependence of $$P$$$$_{5d}$$(3+)/$$P$$$$_{5d}$$(2+) are discussed in terms of hybridization between the conduction electrons and the f electrons.

Journal Articles

New JMTR irradiation test plan on fuels and materials

Nakamura, Takehiko; Nishiyama, Yutaka; Chimi, Yasuhiro; Sasajima, Hideo; Ogiyanagi, Jin; Nakamura, Jinichi; Suzuki, Masahide; Kawamura, Hiroshi

Proceedings of 16th Pacific Basin Nuclear Conference (PBNC-16) (CD-ROM), 6 Pages, 2008/10

In order to maintain and enhance safety of light water reactors in long-term and up-graded operations, proper understanding of irradiation behavior of fuels and materials is essentially important. Japanese government and the Japan Atomic Energy Agency have decided to refurbish the JMTR and to install new tests rigs, in order to play an active role for solving irradiation related issues on plant aging and high-duty uses of the current LWRs and on development of next-generation reactors. New tests on fuel integrity under simulated abnormal transients and high-duty irradiation conditions are planned in the JMTR. Power ramp tests of new design fuel rods will also be performed in the first stage of the program, which is expected to start in year 2011 after refurbishment of the JMTR. Combination of the JMTR tests with simulated reactivity initiated accident tests in the NSRR and loss of coolant accident tests in hot laboratories would serve as the integrated fuel safety research on the high performance fuels at extended burnups, covering from the normal to the accident conditions, including abnormal transients. For the materials irradiation, fracture toughness of reactor vessel steels and stress corrosion cracking behavior of stainless steels are being studied in addition to basic irradiation behavior of nuclear materials such as hafnium. The irradiation studies would contribute not only to solve the current problems but also to identify possible seeds of troubles and to make proactive responses.

Journal Articles

Local modification of hardness in FeCu alloys by using swift heavy ion irradiation

Nakagawa, Sho*; Hori, Fuminobu*; Chimi, Yasuhiro; Ishikawa, Norito; Kitagawa, Michiharu*; Oshima, Ryuichiro*; Tobita, Toru; Taniguchi, Ryoichi*; Suzuki, Masahide; Iwase, Akihiro*

Nuclear Instruments and Methods in Physics Research B, 257(1-2), p.397 - 401, 2007/04

 Times Cited Count:4 Percentile:35.75(Instruments & Instrumentation)

Supersaturated Fe-1.2wt.%Cu alloys were irradiated with 200-MeV Xe and 200-MeV Au ions at elevated temperatures. To make an irradiated region and an unirradiated region in a specimen, a masking plate was put on the specimen during the irradiation. After the irradiation, the hardness was measured by using a conventional microhardness tester or a nano-indenter. We have found that the hardness only in irradiated region increases by the irradiation. The boundary of irradiated and unirradiated regions can be clearly identified by the difference in hardness. The present result implies that swift heavy ion irradiation can be used for the local modification of hardness in supersaturated alloys.

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.

53 (Records 1-20 displayed on this page)