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Journal Articles

High-field depinned phase and planar Hall effect in the skyrmion host Gd$$_2$$PdSi$$_3$$

Hirschberger, M.*; Nakajima, Taro*; Kriener, M.*; Kurumaji, Takashi*; Spitz, L.*; Gao, S.*; Kikkawa, Akiko*; Yamasaki, Yuichi*; Sagayama, Hajime*; Nakao, Hironori*; et al.

Physical Review B, 101(22), p.220401_1 - 220401_6, 2020/06

 Times Cited Count:12 Percentile:92.16(Materials Science, Multidisciplinary)

Journal Articles

Successive phase transitions in $$R_{3}$$Ir$$_{4}$$Sn$$_{13}$$ ($$R$$: La and Ce) investigated using neutron and X-ray diffraction

Nakazato, Seiya*; Iwasa, Kazuaki*; Hashimoto, Daisuke*; Shiozawa, Mami*; Kuwahara, Keitaro*; Nakao, Hironori*; Sagayama, Hajime*; Ishikado, Motoyuki*; Ohara, Takashi; Nakao, Akiko*; et al.

JPS Conference Proceedings (Internet), 30, p.011128_1 - 011128_6, 2020/03

Journal Articles

Magnetic field induced triple-$$q$$ magnetic order in trillium lattice antiferromagnet EuPtSi studied by resonant X-ray scattering

Tabata, Chihiro*; Matsumura, Takeshi*; Nakao, Hironori*; Michimura, Shinji*; Kakihana, Masashi*; Inami, Toshiya*; Kaneko, Koji; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*

Journal of the Physical Society of Japan, 88(9), p.093704_1 - 093704_5, 2019/09

 Times Cited Count:15 Percentile:86.53(Physics, Multidisciplinary)

Journal Articles

Domain structure and electronic state in P3HT:PCBM blend thin films by soft X-ray resonant scattering

Kubota, Masato; Sakurai, Takeaki*; Miyadera, Tetsuhiko*; Nakao, Hironori*; Sugita, Takeshi*; Yoshida, Yuji*

Journal of Applied Physics, 120(16), p.165501_1 - 165501_5, 2016/10

 Times Cited Count:0 Percentile:0(Physics, Applied)

We performed soft X-ray resonant scattering experiments on P3HT:PCBM blend thin films to reveal the domain structure and electronic state, where P3HT and PCBM mean regioregular poly (3-hexylthiophene) and [6,6]-phenyl-C61-buteric acid methyl ester, respectively. We measured two films, where chloroform (CF sample) and 1,2-dichlorobenzene (DCB sample) are used as solvents in the fabrication process. There is negligible X-ray incident angle dependence of the X-ray absorption spectra at the S $$K$$-absorption edge in the CF sample, whereas the DCB sample exhibits clear incident angle dependence. We obtained the wave-number resolved spectra at $mbox{boldmath $Q$}$ = (1, 0, 0) for P3HT molecules in both samples. The packing growth of P3HT molecules is revealed to be much more developed in the DCB sample than the CF sample. In addition, the electronic structure at local sulfur element sites clearly changes for both of the samples.

Journal Articles

Observation of all-in type tetrahedral displacements in nonmagnetic pyrochlore niobates

Torigoe, Shuhei*; Ishimoto, Yutaro*; Aoishi, Yuhei*; Murakawa, Hiroshi*; Matsumura, Daiju; Yoshii, Kenji; Yoneda, Yasuhiro; Nishihata, Yasuo; Kodama, Katsuaki; Tomiyasu, Keisuke*; et al.

Physical Review B, 93(8), p.085109_1 - 085109_5, 2016/02

 Times Cited Count:4 Percentile:26.78(Materials Science, Multidisciplinary)

Journal Articles

Magnetic and electronic properties of (LaMnO$$_3$$)$$_5$$(SrMnO$$_3$$)$$_5$$ superlattice revealed by resonant soft X-ray scattering

Kubota, Masato; Yamada, Hiroyuki*; Nakao, Hironori*; Okamoto, Jun*; Yamasaki, Yuichi*; Sawa, Akihito*; Murakami, Yoichi*

Japanese Journal of Applied Physics, 53(5S1), p.05FH07_1 - 05FH07_5, 2014/05

 Times Cited Count:2 Percentile:10.57(Physics, Applied)

Journal Articles

Antiferromagnetic order of the Co$$^{2+}$$ high-spin state with a large orbital angular momentum in La$$_{1.5}$$Ca$$_{0.5}$$CoO$$_{4}$$

Okamoto, Jun*; Nakao, Hironori*; Yamasaki, Yuichi*; Wadachi, Hiroki*; Tanaka, Arata*; Kubota, Masato; Horigane, Kazumasa*; Murakami, Yoichi*; Yamada, Kazuyoshi*

Journal of the Physical Society of Japan, 83(4), p.044705_1 - 044705_6, 2014/04

 Times Cited Count:7 Percentile:53.57(Physics, Multidisciplinary)

Journal Articles

Spin state of Co$$^{3+} $$ in LaCo$$_{1-x}$$ Rh$$_{x}$$O$$_{3}$$ investigated by structural phenomena

Asai, Shinichiro*; Okazaki, Ryuji*; Terasaki, Ichiro*; Yasui, Yukio*; Kobayashi, Wataru*; Nakao, Akiko*; Kobayashi, Kensuke*; Kumai, Reiji*; Nakao, Hironori*; Murakami, Yoichi*; et al.

Journal of the Physical Society of Japan, 82(11), p.114606_1 - 114606_6, 2013/11

 Times Cited Count:6 Percentile:47.11(Physics, Multidisciplinary)

Neutron and synchrotron X-ray diffraction for LaCo$$_{1-x}$$ Rh$$_{x}$$O$$_{3}$$ have been carried out in order to investigate the structural properties related with the spin state of Co$$^{3+}$$ ions. We have found that the values of the Co(Rh)-O bond lengths in the Co(Rh)O$$_{6}$$ octahedron of LaCo$$_{0.8}$$Rh$$_{0.2}$$O$$_{3}$$ are nearly identical at 10 K. The lattice volume for the Rh$$^{3+}$$ substituted samples decreases with the thermal expansion coefficient similar to that of LaCoO$$_{3}$$ from room temperature, and ceases to decrease around 70 K. These experimental results favor a mixed state consisting of the high-spin state and low-spin state Co$$^{3+}$$ ions, and suggest that the high-spin state Co$$^{3+}$$ ions are thermally excited in addition to those pinned by the substituted Rh$$^{3+}$$ ions.

Journal Articles

Emergent phenomena in perovskite-type manganites

Taguchi, Yasujiro*; Sakai, Hideaki*; Okuyama, Daisuke*; Ishiwata, Shintaro*; Fujioka, Jun*; Fukuda, Tatsuo; Hashizume, Daisuke*; Kagawa, Fumitaka*; Takahashi, Yoichiro*; Shimano, Ryo*; et al.

Physica B; Condensed Matter, 407(11), p.1685 - 1688, 2012/06

 Times Cited Count:4 Percentile:16.62(Physics, Condensed Matter)

Journal Articles

Magnetic phase diagrams of YVO$$_{3}$$ and TbVO$$_{3}$$ under high pressure

Bizen, Daisuke*; Nakao, Hironori*; Iwasa, Kazuaki*; Murakami, Yoichi*; Osakabe, Toyotaka; Fujioka, Jun*; Yasue, Toshio*; Miyasaka, Shigeki*; Tokura, Yoshinori*

Journal of the Physical Society of Japan, 81(2), p.024715_1 - 024715_6, 2012/02

 Times Cited Count:5 Percentile:40.99(Physics, Multidisciplinary)

The magnetic phase diagrams for $$R$$VO$$_{3}$$ ($$R$$ = Y, Tb) were determined by low temperature and high pressure neutron-diffraction techniques. We found that the magnetic ground state in TbVO$$_{3}$$ changes from ${it C}$-type spin ordering (${it C}$-SO) to ${it G}$-type spin ordering (${it G}$-SO) on application of pressure. The transition of the magnetic ground state also indicates that the ground state of the orbital ordering changes from ${it G}$-type orbital ordering (${it G}$-OO) to ${it C}$-type orbital ordering (${it C}$-OO). In YVO$$_{3}$$, the ${it G}$-SO and ${it C}$-OO phases set in simultaneously up to 6.2 GPa, and the disorder-[${it G}$-SO, ${it C}$-OO] phase transition appears above 6 GPa. This is the first observation of a simultaneous spin and orbital order-disorder phase transition in perovskite-type transition-metal oxides $$R$$MO$$_{3}$$. The [${it G}$-SO, ${it C}$-OO] phase is strongly stabilized with increasing pressure, and both the covalency effect and the superexchange interaction play roles in this stabilization.

Journal Articles

X-ray photon correlation spectroscopy of structural fluctuations in relaxor ferroelectrics PZN-9%PT

Owada, Kenji; Shimomura, Susumu*; Nakao, Hironori*; Matsushita, Mitsuyoshi*; Namikawa, Kazumichi*; Mizuki, Junichiro

Journal of Physics; Conference Series, 320, p.012086_1 - 012086_5, 2011/09

 Times Cited Count:0 Percentile:0.03

We have performed an X-ray photon correlation spectroscopy measurement of 91$$%$$Pb(Zn$$_{1/3}$$Nb$$_{2/3}$$)O$$_{3}$$-9$$%$$PbTiO$$_{3}$$ and found a slow structural fluctuation in time near $$T_{rm C}$$. The slow fluctuation consists of long-term and short-term fluctuations. We have derived the short-term fluctuation from the intensity fluctuations and found out the relaxation time to be an order of 10s. It is suggested that the slow fluctuation is owing to the competition between macroscopic tetragonal symmetry and the microscopic orthorhombic symmetry. The competition should be a main reason for the low-frequency dielectric permittivity.

Journal Articles

Contribution of intermediate submicrometer structures to physical properties near $$T$$$$_{rm c}$$ in Pb(Zn$$_{1/3}$$Nb$$_{2/3}$$)O$$_{3}$$-9%PbTiO$$_{3}$$PbTiO$$_{3}$$

Owada, Kenji; Mizuki, Junichiro; Namikawa, Kazumichi*; Matsushita, Mitsuyoshi*; Shimomura, Susumu*; Nakao, Hironori*; Hirota, Kazuma*

Physical Review B, 83(22), p.224115_1 - 224115_7, 2011/06

 Times Cited Count:8 Percentile:39.13(Materials Science, Multidisciplinary)

Complementary use of coherent X-ray diffraction (CXD), X-ray diffuse scattering, conventional X-ray diffraction techniques and dielectric measurements has enabled us to investigate Pb(Zn$$_{1/3}$$Nb$$_{2/3}$$)O$$_{3}$$-9%PbTiO$$_{3}$$ with a multiple-length-scale approach from the macroscale (lattice constants, bulk averaged) and microscale to the nanoscale (polar nanoregions (PNRs)) and discuss the contribution of each scale to the dielectric permittivity.

Journal Articles

X-ray photon correlation spectroscopy study in valence fluctuation compound Eu$$_{3}$$S$$_{4}$$

Nakao, Hironori*; Owada, Kenji; Shimomura, Susumu*; Ochiai, Akira*; Namikawa, Kazumichi*; Mizuki, Junichiro; Mimura, Hidekazu*; Yamauchi, Kazuto*; Murakami, Yoichi*

AIP Conference Proceedings 1234, p.935 - 938, 2010/06

 Times Cited Count:2 Percentile:69.52

Journal Articles

X-ray intensity fluctuation spectroscopy using nanofocused hard X-rays; Its application to study of relaxor ferroelectrics

Owada, Kenji; Namikawa, Kazumichi*; Shimomura, Susumu*; Nakao, Hironori*; Mimura, Hidekazu*; Yamauchi, Kazuto*; Matsushita, Mitsuyoshi*; Mizuki, Junichiro

Japanese Journal of Applied Physics, 49(2), p.020216_1 - 020216_3, 2010/02

 Times Cited Count:3 Percentile:16.27(Physics, Applied)

Journal Articles

Structural phase transition in the spin gap system YbAl$$_3$$C$$_3$$

Matsumura, Takeshi*; Inami, Toshiya; Kosaka, Masashi*; Kato, Yoshiaki*; Inukai, Takaki*; Ochiai, Akira*; Nakao, Hironori*; Murakami, Yoichi*; Katano, Susumu*; Suzuki, Hiroyuki*

Journal of the Physical Society of Japan, 77(10), p.103601_1 - 103601_4, 2008/10

 Times Cited Count:12 Percentile:59.32(Physics, Multidisciplinary)

Journal Articles

Devil's flower resulting from a successive charge disproportionation of NaV$$_{2}$$O$$_{5}$$; Understanding of the details of the Ising spin and the competitive interactions which made the devil's flower bloom

Owada, Kenji; Fujii, Yasuhiko; Muraoka, Jiro*; Nakao, Hironori*; Murakami, Yoichi*; Noda, Yukio*; Osumi, Hiroyuki*; Ikeda, Naoshi*; Shobu, Takahisa; Isobe, Masahiko*; et al.

Hoshako, 21(2), p.87 - 96, 2008/03

Devil's flower has been found in a temperature-pressure phase diagram of NaV$$_{2}$$O$$_{5}$$, which shows a charge disproportionation (CD) at ambient pressure. By a complementary use of an X-ray structural analysis and a resonant X-ray diffraction, which is sensitive to CD, we have investigated the structural relationship between two ground states appeared in lower and higher pressure regions including the charge arrangements. It has been clarified that two equivalent types of charge arrangement in CD correspond to the Ising variable in NaV$$_{2}$$O$$_{5}$$. The atomic shifts are regarded as linearly coupled to the Ising spins. The results lead us to the conclusion that it is the first time that the devil's flower blooms in a charge-disproportionation system. The results also lead us to a hypothesis that the competitive interactions between a Ising spins may result from the Ising spin-phonon coupling.

Journal Articles

Structural relations between two ground states of NaV$$_{2}$$O$$_{5}$$ under high pressure; A Synchrotron X-ray diffraction study

Owada, Kenji; Fujii, Yasuhiko; Muraoka, Jiro*; Nakao, Hironori*; Murakami, Yoichi; Noda, Yukio*; Osumi, Hiroyuki*; Ikeda, Naoshi*; Shobu, Takahisa; Isobe, Masahiko*; et al.

Physical Review B, 76(9), p.094113_1 - 094113_10, 2007/09

 Times Cited Count:10 Percentile:46.38(Materials Science, Multidisciplinary)

Structural relations between two ground states of the ANNNI (Axial Next Nearest Neighbor Ising) compound NaV$$_{2}$$O$$_{5}$$, C$$_{1/4}$$- and C$$_{0}$$-phases below and above the transition pressure $$P_{rm C}$$ = 1 GPa, were investigated by X-ray diffraction and scattering techniques. The structure of the C$$_{0}$$-phase is well explained by the $$A$$($$A'$$) pattern which is one of four layers ($$AAA'A'$$) of the C$$_{1/4}$$-phase, however, the amount of the atomic shifts under the conditions 1.6 GPa and 6 K is 27% that under ambient pressure. On the other hand, resonant X-ray scattering showed that the charges are disproportionated under high pressure. Based on these facts, it was concluded that charge disproportionation corresponds to the Ising variable in NaV$$_{2}$$O$$_{5}$$, where the atomic shifts are regarded as linearly coupled to the Ising spins. These results lead to the hypothesis that the competitive interactions between the Ising spins may result from the Ising spin-phonon coupling.

Journal Articles

Resonant X-ray magnetic diffraction experiments on SmB$$_2$$C$$_2$$

Inami, Toshiya; Homma, Tetsuo*; Tsutsui, Satoshi*; Indo, Kentaro*; Onodera, Hideya*; Ishii, Kenji; Owada, Kenji; Kuzushita, Kaori*; Nakao, Hironori*; Murakami, Yoichi*

Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.748 - 750, 2007/03

We investigated successive phase transitions in SmB$$_2$$C$$_2$$ at $$T_{rm N2}$$=37K and $$T_{rm N1}$$=51K by means of resonant X-ray diffraction. Strong resonant diffraction signal is observed at the 101 reflection below $$T_{rm N2}$$ at the Sm $$L_3$$ edge, whereas in the intermediate phase signals appear at incommensurate positions $${vec Q}$$=(1$$pmdelta$$, $$pmdelta$$,1) where $$delta$$=0.13. Accordingly, the successive phase transitions in SmB$$_2$$C$$_2$$ is found to be commensurate-to-incommensurate magnetic phase transitions.

Journal Articles

Coherent X-ray diffraction for domain observation

Owada, Kenji; Namikawa, Kazumichi; Mizuki, Junichiro; Shimomura, Susumu*; Nakao, Hironori*; Ito, Kazuki*; Matsushita, Mitsuyoshi*; Yoneda, Yasuhiro; Murakami, Yoichi*; Hirota, Kazuma*

Transactions of the Materials Research Society of Japan, 32(1), p.7 - 10, 2007/03

An X-ray speckle pattern well reflects a particle or domain alignment on the inside of materials. Detecting the alignment is important for understanding a function of the materials such as ferroelectric, piezoelectric materials, photonic crystals and so on. We have thus constructed the apparatus for coherent X-ray diffraction at BL22XU@SPring-8, high quality slits for obtaining the full coherent X-ray beam, high resolution X-ray CCD camera for obtaining the well-resolved speckle pattern, and so on. By using the devices, we have successfully observed the speckle pattern from Cu$$_{3}$$Au, the ferroelectric material PZN-9%PT (91%Pb(Zn$$_{1/3}$$Nb$$_{2/3}$$)O$$_{3}$$-9%PbTiO$$_{3}$$) and Sr-doped BaTiO$$_{3}$$. The 2DFFT image gives us a spatial autocorrelation function which includes the information of the arrangement of the domains in the crystal within micrometers scale.

Journal Articles

Discovery of the "Devil's flower" in a charge-ordering system; Synchrotron X-ray diffraction study of NaV$$_{2}$$O$$_{5}$$

Owada, Kenji; Fujii, Yasuhiko; Nakao, Hironori*; Murakami, Yoichi*; Isobe, Masahiko*; Ueda, Yutaka*

Modern Physics Letters B, 20(5), p.199 - 214, 2006/02

 Times Cited Count:5 Percentile:22.87(Physics, Applied)

We review recent synchrotron diffraction studies of NaV$$_{2}$$O$$_{5}$$. The resonant X-ray scattering performed on a monoclinically-split single domain of NaV$$_{2}$$O$$_{5}$$ shows a critically enhanced contrast between V$$^{4+}$$ and V$$^{5+}$$ ions. The results has led us to the unequivocal conclusion of the charge-order pattern of low-temperature phase of NaV$$_{2}$$O$$_{5}$$ below $$T_{rm c}$$ = 35 K. In spite of the possible four types of configuration of the zig-zag-type charge-order patterns in the $$ab$$-plane (A, A', B and B'), the stacking sequence along the $$c$$-axis is determined as the AAA'A' type by comparison with model calculations. By assigning the A and A' configurations to Ising spins $$uparrow$$ and $$downarrow$$, one can reasonably explain the previously discovered "devil's staircase"-type behavior with respect to the modulation of layer-stacking sequences at high pressures and low temperatures, which clearly resembles the global phase diagram theoretically predicted by the ANNNI model, called "devil's flower". This is the first case that the devil's flower appears in such a charge-ordering system, where charge-order patterns are regarded as Ising spins.

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