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Journal Articles

Spin gap in the weakly interacting quantum spin chain antiferromagnet KCuPO$$_{4}$$$$cdot$$H$$_{2}$$O

Fujihara, Masayoshi; Hagihara, Masato; Morita, Katsuhiro*; Murai, Naoki; Koda, Akihiro*; Okabe, Hirotaka*; Mitsuda, Setsuo*

Physical Review B, 107(5), p.054435_1 - 054435_8, 2023/02

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

The $$S$$ = 1/2 Heisenberg linear chain antiferromagnet is the simplest spin model; nevertheless it serves as a platform for various quantum many-body phenomena. Here, we report the magnetic behavior of a quasi-one-dimensional antiferromagnet KCuPO$$_{4}$$$$cdot$$H$$_{2}$$O. A long-range commensurate antiferromagnetic order with ordered moment 0.31(1) $$mu_{rm{B}}$$ per spin occurs at $$T_{rm{N}}$$ = 11.7(1) K. Above $$T_{rm{N}}$$, the inelastic neutron excitation is characterized by a two spinon continuum. The intrachain interaction $$J$$ and interchain interaction $$|J'|$$ are estimated to be 172 K and 4.25(4) K, respectively; thus the ratio of the $$|J'|$$/$$J$$ = 0.0247(3). At lower energies, below $$T_{rm{N}}$$, a spin gap is observed in the dispersive excitations. These results are consistent with characteristics observed in weakly interacting $$S$$ = 1/2 Heisenberg chain system.

Journal Articles

Birchite Cd$$_{2}$$Cu$$_{2}$$(PO$$_{4}$$)$$_{2}$$SO$$_{4}$$ $$cdot$$ 5H$$_{2}$$O as a model antiferromagnetic spin-1/2 Heisenberg $${it J}$$$$_{1}$$-$${it J}$$$$_{2}$$ chain

Fujihara, Masayoshi; Jeschke, H. O.*; Morita, Katsuhiro*; Kuwai, Tomohiko*; Koda, Akihiro*; Okabe, Hirotaka*; Matsuo, Akira*; Kindo, Koichi*; Mitsuda, Setsuo*

Physical Review Materials (Internet), 6(11), p.114408_1 - 114408_8, 2022/11

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

$${it S}$$ = 1/2 Heisenberg $${it J}$$$$_{1}$$-$${it J}$$$$_{2}$$ chain antiferromagnets have been investigated extensively due to their exotic magnetic states. Here, we report the magnetic behavior of birchite Cd$$_{2}$$Cu$$_{2}$$(PO$$_{4}$$)$$_{2}$$SO$$_{4}$$$$cdot$$5H$$_{2}$$O and its effective spin model. Experimental studies by magnetic susceptibility, magnetization, heat capacity, and $$mu$$SR measurements indicate the absence of long-range order down to 0.4 K. Theoretical studies reveal that birchite is a model compound for the $${it J}$$$$_{1}$$-$${it J}$$$$_{2}$$ antiferromagnetic chain: the intrachain interactions $${it J}$$$$_{1}$$ and $${it J}$$$$_{2}$$ are antiferromagnetic and their magnitude is about 100 times larger than the interchain interactions. The magnitude of $${it J}$$$$_{2}$$ is two to three times larger than that of $${it J}$$$$_{1}$$, thus the spin gap is expected to be only a few percent of that of $${it J}$$$$_{1}$$. The temperature dependence of the specific heat shows a broad peak at about 1 K ($$simeq$$ 0.036 $${it J}$$$$_{1}$$), which suggests the presence of a spin gap.

Journal Articles

Gapless spin liquid in a square-kagome lattice antiferromagnet

Fujihara, Masayoshi*; Morita, Katsuhiro*; Mole, R.*; Mitsuda, Setsuo*; Toyama, Takami*; Yano, Shinichiro*; Yu, D.*; Sota, Shigetoshi*; Kuwai, Tomohiko*; Koda, Akihiro*; et al.

Nature Communications (Internet), 11, p.3429_1 - 3429_7, 2020/07

 Times Cited Count:25 Percentile:89.71(Multidisciplinary Sciences)

Journal Articles

Hardness modification of aluminum-alloys by means of energetic ion irradiation and subsequent thermal aging

Mitsuda, Tomoaki*; Kobayashi, Ippei*; Kosugi, Shinya*; Fujita, Naoki*; Saito, Yuichi; Hori, Fuminobu*; Semboshi, Satoshi*; Kaneno, Yasuyuki*; Nishida, Kenji*; Soneda, Naoki*; et al.

Nuclear Instruments and Methods in Physics Research B, 272, p.49 - 52, 2012/02

 Times Cited Count:7 Percentile:52.71(Instruments & Instrumentation)

Journal Articles

Hardening of Al-Cu-Mg alloy by energetic ion irradiation

Mitsuda, Tomoaki*; Kobayashi, Ippei*; Kosugi, Shinya*; Fujita, Naoki*; Saito, Yuichi; Hori, Fuminobu*; Semboshi, Satoshi*; Kaneno, Yasuyuki*; Nishida, Kenji*; Soneda, Naoki*; et al.

Journal of Nuclear Materials, 408(2), p.201 - 204, 2011/01

 Times Cited Count:11 Percentile:66.95(Materials Science, Multidisciplinary)

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:11 Percentile:46.2(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.

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

Status and perspective of the Nb$$_{3}$$Al development

Takeuchi, Takao*; Kikuchi, Akihiro*; Banno, Nobuya*; Kitaguchi, Hitoshi*; Iijima, Yasuo*; Tagawa, Kohei*; Nakagawa, Kazuhiko*; Tsuchiya, Kiyosumi*; Mitsuda, Shiori*; Koizumi, Norikiyo; et al.

Cryogenics, 48(7-8), p.371 - 380, 2008/07

 Times Cited Count:60 Percentile:87.78(Thermodynamics)

Nb$$_{3}$$Al has advantages of better tolerance to strain/stress and a higher critical magnetic field (30 T at 4.2 K) for stoichiometric composition over Nb$$_{3}$$Sn. The rapid-heating, quenching and transformation annealing (RHQT) process enables to form a stoichiometric Nb$$_{3}$$Al with fine grain structures via metastable bcc supersaturated-solid-solution. As a result a large critical current density of Nb$$_{3}$$Al is achieved over the whole range of magnetic fields without trading off the excellent strain tolerance. A long-length of RHQ processing has been established, and a rectangular but Cu stabilized Nb$$_{3}$$Al strand is about be commercially available for NMR uses. Ag or Cu internal stabilization and Cu ion-plating/electroplating techniques have been also developed to enable the stabilized round wire for accelerator and fusion magnets. Successfully energized test coils that were manufactured with a wind-and-react technique have demonstrated that a long piece of Cu stabilized RHQT Nb$$_{3}$$Al wire is really available for practical applications.

Journal Articles

High-magnetic-field X-ray absorption spectroscopy of field-induced valence transition in EuNi$$_2$$(Si$$_{1-x}$$Ge$$_x$$)$$_2$$

Matsuda, Yasuhiro*; Inami, Toshiya; Owada, Kenji; Murata, Yuto*; Nojiri, Hiroyuki*; Murakami, Yoichi*; Mitsuda, Akihiro*; Wada, Hirofumi*; Miyazaki, Hiroshi*; Harada, Isao*

Journal of the Physical Society of Japan, 77(5), p.054713_1 - 054713_7, 2008/05

 Times Cited Count:25 Percentile:74.48(Physics, Multidisciplinary)

The magnetic-field-induced valence transition in EuNi$$_2$$(Si$$_{1-x}$$Ge$$_x$$)$$_2$$ (x=0.82, 0.85) has been studied by X-ray absorption spectroscopy at low temperatures. The field dependence of the Eu valence is directly observed for the first time. We find a significant decrease in the valences at high magnetic fields above 40 T. The valence of Eu changes from v = 2.75 at a zero field to v = 2.33 at 40 T for x = 0.82. The results are analyzed using a theoretical model. The hybridization parameter V between the Eu$$^{2+}$$ and Eu$$^{3+}$$ states and the energy separation $$Delta$$$$E$$ are determined, which are crucial for quantum mechanical mixing.

Journal Articles

Application of miniature pulsed magnets to synchrotron X-ray spectroscopy and neutron diffraction

Matsuda, Yasuhiro*; Murata, Yuto*; Inami, Toshiya; Owada, Kenji; Nojiri, Hiroyuki*; Oyama, Kenji*; Kato, Naoki*; Murakami, Yoichi*; Iga, Fumitoshi*; Takabatake, Toshiro*; et al.

Journal of Physics; Conference Series, 51, p.490 - 493, 2006/00

 Times Cited Count:8 Percentile:92.41

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 on the charge ordering transitions in the mixed valent compound EuPtP

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

no journal, , 

Oral presentation

X-ray Raman scattering experiment on the valence transition of EuPd$$_2$$Si$$_2$$

Inami, Toshiya; Ishii, Kenji; Jarrige, I.; Yoshida, Masahiro; Mitsuda, Akihiro*

no journal, , 

Oral presentation

X-ray Raman scattering study on the valence transition of EuPd$$_2$$Si$$_2$$

Inami, Toshiya; Ishii, Kenji; Yoshida, Masahiro; Mitsuda, Akihiro*; Taguchi, Munetaka*; Shin, S.*

no journal, , 

no abstracts in English

Oral presentation

Hardening of Al-Cu-Mg alloy by energetic ion irradiation

Mitsuda, Tomoaki*; Iwase, Akihiro*; Saito, Yuichi

no journal, , 

no abstracts in English

Oral presentation

X-ray Raman scattering study on the valence transition of EuPd$$_2$$Si$$_2$$, 2

Inami, Toshiya; Ishii, Kenji; Jarrige, I.; Mitsuda, Akihiro*

no journal, , 

no abstracts in English

Oral presentation

X-ray Raman scattering study on the valence transition in EuPd$$_2$$Si$$_2$$

Inami, Toshiya; Ishii, Kenji; Jarrige, I.*; Yoshida, Masahiro*; Mitsuda, Akihiro*

no journal, , 

X-ray absorption spectroscopy at the lanthanoid $$M$$- and $$N$$-edges is a versatile tool for investigating valency, spatial symmetry and hybridization of the $$4f$$ electrons. A disadvantage of this technique, however, is the very short penetration length of soft X-rays in solid materials. X-ray Raman scattering (XRS) is an alternative method to obtain absorption spectra. High energy incident X-rays transfer a part of their energy to various excitations and the obtained energy-loss spectrum corresponds to an absorption spectrum. Because of the high penetration depth of hard X-rays, this technique is truly bulk sensitive. Here we report on a feasibility study of XRS experiments applied to a mixed-valent f-electron system. The test sample was EuPd$$_2$$Si$$_2$$, which exhibits a sharp and large valence transition around 150 K. The obtained XRS spectra showed clear absorption features at the $$M$$- and $$N$$-edges. However, we did not detect any difference between the spectra at 10 K and 200 K.

Oral presentation

Magnetic properties of checkerboard lattice antiferromagnet KCuPO$$_4$$H$$_2$$O

Fujihara, Masayoshi; Morita, Katsuhiro*; Mitsuda, Setsuo*; Okabe, Hirotaka*; Koda, Akihiro*; Murai, Naoki; Hagihara, Masato

no journal, , 

no abstracts in English

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