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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

Large ferroquadrupole moment induced in the octupole-ordered Ce$$_{0.7}$$La$$_{0.3}$$B$$_6$$ revealed by high-resolution X-ray diffraction

Inami, Toshiya; Michimura, Shinji*; Hayashi, Yuya*; Matsumura, Takeshi*; Sera, Masafumi*; Iga, Fumitoshi*

Physical Review B, 90(4), p.041108_1 - 041108_5, 2014/07

 Times Cited Count:9 Percentile:43.94(Materials Science, Multidisciplinary)

We carried out a high-resolution X-ray diffraction experiment on Ce$$_{0.7}$$La$$_{0.3}$$B$$_6$$. This compound exhibits antiferro-octupole order (AFO) below $$T_O$$ = 1.4 K, and it is theoretically suggested that ferroquadrupole moments and a resultant rhombohedral deformation are induced in the AFO phase. We observe the splitting of Bragg reflections below $$T_O$$ and find that the unit cell is rhombohedral with the elongated [111] axis. We also precisely evaluate the magnitude of the induced quadrupole moments from the obtained shear strain and find that the quadrupole moments are not reduced in the AFO phase.

Journal Articles

Valence state in Ce-based heavy fermion compounds at high magnetic fields

Matsuda, Yasuhiro*; Her, J.-L.*; Michimura, Shinji*; Inami, Toshiya; Ebihara, Takao*; Amitsuka, Hiroshi*

JPS Conference Proceedings (Internet), 3, p.011044_1 - 011044_6, 2014/06

Synchrotron X-ray absorption spectroscopy of CeRh$$_2$$Si$$_2$$ has been performed in pulsed high magnetic fields of up to 32 T. The Ce valence is slightly larger than 3+ at 5 K and decreases with increasing magnetic above 20 T. The field-induced valence change seems to correspond to the metamagnetic transition in the magnetization process. This phenomena is similar to our previous result on CeRu$$_2$$Si$$_2$$ and seems to be common in Ce-based heavy fermion compounds.

Journal Articles

Multipole order and fluctuation in Ce$$_{0.7}$$La$$_{0.3}$$B$$_6$$ studied by resonant X-ray diffraction

Matsumura, Takeshi*; Michimura, Shinji*; Inami, Toshiya; Otsubo, Toru*; Tanida, Hiroshi*; Iga, Fumitoshi*; Sera, Masafumi*

JPS Conference Proceedings (Internet), 3, p.014008_1 - 014008_6, 2014/06

We study the $$T_{beta}$$-type antiferro-octupole (AFO) ordered state of Ce$$_{0.7}$$La$$_{0.3}$$B$$_6$$ below 1.5 K by resonant X-ray diffraction in magnetic fields. Multipole moments induced by the field in the AFO phase are identified. In a mean-field model for the $$T_{beta}$$ AFO order within the $$Gamma_8$$ quartet crystal-field ground state, the $$O_{22}$$ and $$O_{20}$$ antiferroquadrupoles (AFQ) are expected as mostly induced AFQ. However, in contrast to this expectation, the main induced moment is found to be the $$O_{xy}$$-type AFQ.

Journal Articles

Magnetic-field-induced charge order in the filled skutterudite SmRu$$_{4}$$P$$_{12}$$; Evidence from resonant and nonresonant X-ray diffraction

Matsumura, Takeshi*; Michimura, Shinji*; Inami, Toshiya; Hayashi, Yuya*; Fushiya, Kengo*; Matsuda, Tatsuma*; Higashinaka, Ryuji*; Aoki, Yuji*; Sugawara, Hitoshi*

Physical Review B, 89(16), p.161116_1 - 161116_5, 2014/04

 Times Cited Count:14 Percentile:58.55(Materials Science, Multidisciplinary)

The antiferromagnetic ordered phase below $$T_{rm MI}$$ = 16.5 K and the unresolved intermediate phase between $$T_{rm MI}$$ and $$T^*$$ (= 14 K) in SmRu$$_4$$P$$_{12}$$ have been studied by resonant and nonresonant X-ray diffraction. In the intermediate phase, nonresonant Thomson scattering with $$q$$ = (1,0,0) is induced by applying a magnetic field. This phenomena is caused by atomic displacements reflecting the charge order in the $$p$$ band, as predicted theoretically. Simultaneously, the antiferromagnetic moment of Sm is enhanced along the field direction, which is considered to reflect the staggered ordering of the $$Gamma_7$$ - $$Gamma_8$$ crystal-field states. The present results show that the orbital-dependent $$p$$ - $$f$$ hybridization in association with the nesting instability in the $$p$$ band gives rise to the unconventional charge order similarly with PrRu$$_4$$P$$_{12}$$ and PrFe$$_4$$P$$_{12}$$.

Journal Articles

Evidence for hidden quadrupolar fluctuations behind the octupole order in Ce$$_{0.7}$$La$$_{0.3}$$B$$_6$$ from resonant X-ray diffraction in magnetic fields

Matsumura, Takeshi*; Michimura, Shinji*; Inami, Toshiya; Otsubo, Toru*; Tanida, Hiroshi*; Iga, Fumitoshi*; Sera, Masafumi*

Physical Review B, 89(1), p.014422_1 - 014422_13, 2014/01

 Times Cited Count:12 Percentile:53.39(Materials Science, Multidisciplinary)

The multipole ordered phase in Ce$$_{0.7}$$La$$_{0.3}$$B$$_6$$ (phase IV) has been studied by resonant X-ray diffraction in magnetic fields. By utilizing diamond X-ray phase plates to rotate the incident linear polarization and a conventional crystal analyzer system, full linear polarization analysis has been performed to identify the order parameters. The analysis shows that the $$Gamma_{rm 5g}$$ quadrupoles are more induced by the field than the $$Gamma_{rm 3g}$$ quadrupoles in phase IV, in disagreement with mean-field calculations, in which the $$Gamma_{rm 3g}$$ quadrupole is the main induced moment. Hence, we consider that large fluctuations of the $$Gamma_{rm 5g}$$ quadrupole is hidden behind the primary ordering of the octupole.

Journal Articles

X-ray backscattering study of crystal lattice distortion in hidden order of URu$$_2$$Si$$_2$$

Tabata, Chihiro*; Inami, Toshiya; Michimura, Shinji*; Yokoyama, Makoto*; Hidaka, Hiroyuki*; Yanagisawa, Tatsuya*; Amitsuka, Hiroshi*

Philosophical Magazine, 94(32-33), p.3691 - 3701, 2014/00

 Times Cited Count:14 Percentile:64.03(Materials Science, Multidisciplinary)

Journal Articles

Temperature and magnetic field dependent Yb valence in YbRh$$_2$$Si$$_2$$ observed by X-ray absorption spectroscopy

Nakai, Hirohito*; Ebihara, Takao*; Tsutsui, Satoshi*; Mizumaki, Masaichiro*; Kawamura, Naomi*; Michimura, Shinji*; Inami, Toshiya; Nakamura, Toshiyuki*; Kondo, Akihiro*; Kindo, Koichi*; et al.

Journal of the Physical Society of Japan, 82(12), p.124712_1 - 124712_5, 2013/12

 Times Cited Count:7 Percentile:51.13(Physics, Multidisciplinary)

The temperature and magnetic field dependences of Yb valence were observed in the heavy fermion compoundYbRh$$_2$$Si$$_2$$ by X-ray absorption spectroscopy. The measurements revealed that the Yb valence decreases with decreasing temperature in the range from 200 to 2 K and increases with increasing magnetic field in the range from 0 to 33 T without showing an abrupt change in the Yb valence. The Yb valence is in the range from 2.92 to 2.96 depending on temperature and magnetic field. With respect to the valence being 2.92 at 0 T and 2.93 at 33 T in 2 K, YbRh$$_2$$Si$$_2$$ is a valence fluctuation compound and does not reach the integer trivalent state at high magnetic field. These results endorse the conventional knowledge that the valence of Yb is very close to the integer value of 3+, decreases with decreasing temperature, and becomes closer to 3+ with increasing magnetic field.

Journal Articles

Synchrotron X-ray spectroscopy study on the valence state in $$alpha$$- and $$beta$$-TbAlB$$_4$$ at low temperature and high magnetic fields

Matsuda, Yasuhiro*; Nakamura, Toshiyuki*; Kuga, Kentaro*; Nakatsuji, Satoru*; Michimura, Shinji*; Inami, Toshiya; Kawamura, Naomi*; Mizumaki, Masaichiro*

Journal of the Korean Physical Society, 62(12), p.1778 - 1781, 2013/06

 Times Cited Count:9 Percentile:57.28(Physics, Multidisciplinary)

The valence state of Yb ions in $$alpha$$- and $$beta$$-YbAlB$$_4$$ has been investigated by X-ray absorption and emission spectroscopy at temperatures from 2 to 280 K. It is found that the valence gradually increases with increasing temperature toward 3+ and that the characteristic temperature of the valence fluctuations is about 290 K. We also observe a small increase in the Yb valence ($$sim$$ 0.002) in $$beta$$-YbAlB$$_4$$ by a magnetic field of 32 T at 40 K.

Journal Articles

Double phase-plate setup for chromatic aberration compensation for resonant X-ray diffraction experiments

Inami, Toshiya; Michimura, Shinji*; Matsumura, Takeshi*

Journal of Physics; Conference Series, 425(13), p.132011_1 - 132011_5, 2013/03

 Times Cited Count:5 Percentile:90.69

Resonant X-ray diffraction is a powerful tool for detecting ordered structures of charge, magnetic and orbital degrees of freedom. The symmetry of an order parameter is determined by changing the relative orientation between the polarization of incident X-rays and the order parameter. A new method suited for extreme conditions is performed by rotating the incident polarization using a diamond phase plate. A disadvantage of this method is significant loss in intensity for low-energy X-rays. In order to obtain both a high degree of linear polarization and strong X-ray intensity, we have constructed optics that compensates chromatic aberration using two diamond phase plates. In a test experiment in beamline BL22XU at SPring-8, two 300 microns diamond phase plates were used. The obtained linear polarization reached more than 96% at 6.15 keV, showing marked improvement compared to the linear polarization 90% obtained by a single 500 microns phase plate.

Journal Articles

Structural investigation of magnetocapacitive SmMnO$$_3$$

Maeda, Hiroki*; Ishiguro, Yuki*; Honda, Takashi*; Jung, J.-S.*; Michimura, Shinji*; Inami, Toshiya; Kimura, Tsuyoshi*; Wakabayashi, Yusuke*

Journal of the Ceramic Society of Japan, 121(3), p.265 - 267, 2013/03

 Times Cited Count:2 Percentile:17.12(Materials Science, Ceramics)

Structural deformation of a magnetocapacitive material SmMnO$$_3$$ was studied by X-ray diffraction measurement in a magnetic field. This antiferromagnetic material shows a jump in dielectric constant at 9 K only when a magnetic field of a few tesla is applied. In-field X-ray diffraction measurements clarified that there is no sudden change in structure that involves atomic displacement within the c-plane in Pbnm notation, while the antiferromagnetic phase transition at 60 K gives rise to a noticeable rotation of the MnO$$_6$$ octahedra. This rotation occurs to maximize the energy gain through the exchange interaction.

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:60.72(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

Suppression of $$f$$-electron itinerancy in CeRu$$_2$$Si$$_2$$ by a strong magnetic field

Matsuda, Yasuhiro*; Nakamura, Toshiyuki*; Her, J. L.*; Michimura, Shinji*; Inami, Toshiya; Kindo, Koichi*; Ebihara, Takao*

Physical Review B, 86(4), p.041109_1 - 041109_4, 2012/07

 Times Cited Count:9 Percentile:41.97(Materials Science, Multidisciplinary)

The valence state of Ce in a typical heavy fermion compound CeRu$$_2$$Si$$_2$$ has been investigated by synchrotron X-ray absorption spectroscopy at 1.8 K in high magnetic fields of up to 40T. The valence was slightly larger than for the pure trivalent state, as expected in heavy fermion compounds, and it decreased toward the trivalent state as the magnetic field was increased. The field-induced valence reduction indicates that the itinerant character of the 4$$f$$ electrons in CeRu$$_2$$Si$$_2$$ was suppressed by a strong magnetic field. The suppression was gradual and showed a characteristic magnetic field dependence, which reflects the metamagnetism around $$H_{rm m}$$ $$sim$$ 8T.

Journal Articles

Resonant X-ray diffraction study of multipole ordering in the ferromagnetic compound CePd$$_3$$S$$_4$$

Michimura, Shinji*; Inami, Toshiya; Matsuoka, Eiichi*; Watahiki, Masanori*; Tanigaki, Katsumi*; Onodera, Hideya*

Journal of the Physical Society of Japan, 81(4), p.044711_1 - 044711_5, 2012/04

 Times Cited Count:4 Percentile:35.45(Physics, Multidisciplinary)

Resonant X-ray diffraction experiments on CePd$$_3$$S$$_4$$ were performed at the Ce-$$L$$$$_{3}$$ absorption edge to study the states of quadrupolar ordering below the ferromagnetic transition temperature $$T_{rm C}$$ = 6.3 K. The magnetic structure of CePd$$_3$$S$$_4$$ was reported as a canted ferromagnetic structure with a canting angle of 51$$^circ$$. It has therefore been pointed out that the complex magnetic structure arises from the simultaneous ordering of quadrupole moments. We observed the azimuthal angle dependence of the diffraction intensity of the two forbidden reflections 003 and 104 reflections for both $$pi$$-$$pi$$' and $$pi$$-$$sigma$$' scattering processes. The results revealed that $$O$$$$_2$$$$^{0}$$-type antiferroquadrupolar ordering coexists with magnetic ordering. We infer that the magnetic structure of CePd$$_3$$S$$_4$$ is not a canted structure but a ferrimagnetic structure and that the quadrupole moment is also a primary-order parameter.

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:10 Percentile:58.4(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:20 Percentile:66.65(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

Observation of two charge ordering transitions in the valence-fluctuating EuPtP by resonant X-ray diffraction

Inami, Toshiya; Michimura, Shinji; Mitsuda, Akihiro*; Wada, Hirofumi*

Physical Review B, 82(19), p.195133_1 - 195133_5, 2010/11

 Times Cited Count:10 Percentile:46.13(Materials Science, Multidisciplinary)

Two first-order phase transitions of the valence-fluctuating compound EuPtP at $$T_1$$=246 K and $$T_2$$=200 K were examined by means of resonant X-ray diffraction at the Eu $$L_3$$ absorption edge. Although previous M$"o$ssbauer spectroscopy and preliminary X-ray diffraction experiments have suggested charge ordered states, characteristic energy spectra of the 111 and 11$$frac{2}{3}$$ reflections observed in the present experiment unambiguously indicated that twofold and threefold superstructures of Eu valence exist below $$T_2$$ and between $$T_1$$ and $$T_2$$, respectively. We also propose a mechanism to explain the charge ordering in EuPtP based on a charge-lattice coupling that alters a Coulomb repulsion.

Oral presentation

Valence transition and ordered valency in EuPtP

Inami, Toshiya; Michimura, Shinji; Mitsuda, Akihiro*; Wada, Hirofumi*

no journal, , 

no abstracts in English

Oral presentation

Resonant X-ray diffraction study of a multipole ordering in CePd$$_3$$S$$_4$$

Michimura, Shinji; Inami, Toshiya; Matsuoka, Eiichi*; Watahiki, Masanori*; Tanigaki, Katsumi*; Onodera, Hideya*

no journal, , 

no abstracts in English

Oral presentation

Resonant X-ray diffraction study on the charge ordering transitions in the mixed valent compound EuPtP

Inami, Toshiya; Michimura, Shinji; Mitsuda, Akihiro*; Wada, Hirofumi*

no journal, , 

29 (Records 1-20 displayed on this page)