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Journal Articles

Local atomic displacements and sign of the structural transformation in medium-entropy alloys observed in extended X-ray absorption fine structure spectra

Ikeda, Yoichi*; Umemoto, Yoshihiko*; Matsumura, Daiju; Tsuji, Takuya; Hashimoto, Yuki*; Kitazawa, Takafumi*; Fujita, Masaki*

Materials Transactions, 64(9), p.2254 - 2260, 2023/09

https://doi.org/10.2320/matertrans.MT-M2023043
 Times Cited Count：4 Percentile：44.33(Materials Science, Multidisciplinary)

Journal Articles

Observation of field-induced single-ion magnetic anisotropy in a multiorbital Kondo alloy (Lu,Yb)Rh$$_2$$Zn$$_{20}$$

Kitazawa, Takafumi; Ikeda, Yoichi*; Sakakibara, Toshiro*; Matsuo, Akira*; Shimizu, Yusei*; Tokunaga, Yo; Haga, Yoshinori; Kindo, Koichi*; Nambu, Yusuke*; Ikeuchi, Kazuhiko*; et al.

Physical Review B, 108(8), p.085105_1 - 085105_7, 2023/08

https://doi.org/10.1103/PhysRevB.108.085105
 Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)

Journal Articles

Molecular magnetism in neptunyl(+1,+2) complexes; $$^{237}$$Np-M$"o$ssbauer and magnetic study

Nakamura, Akio; Nakada, Masami; Nakamoto, Tadahiro*; Kitazawa, Takafumi*; Takeda, Masuo*

Journal of Alloys and Compounds, 444-445, p.621 - 633, 2007/10

https://doi.org/10.1016/j.jallcom.2006.12.062
 Times Cited Count：3 Percentile：27.44(Chemistry, Physical)

no abstracts in English

Journal Articles

Magnetic property of neptunyl (+2) complex NpO$$_{2}$$(C$$_{6}$$H$$_{7}$$O$$_{2}$$)$$_{2}$$(C$$_{5}$$H$$_{5}$$N)

Nakamura, Akio; Nakada, Masami; Nakamoto, Tadahiro*; Kitazawa, Takafumi*; Takeda, Masuo*

Journal of Magnetism and Magnetic Materials, 310(2, Part2), p.1447 - 1449, 2007/03

Magnetic property of a nitrogen (N)-coordinated neptunyl (+2) (Np(VI)) complex. 1 NpO$$_{2}$$(acac)$$_{2}$$(py) (acac=C$$_{6}$$H$$_{7}$$O$$_{2}$$, py=C$$_{5}$$H$$_{5}$$N) was studied by DC magnetization (M) measurements. While previous $$^{237}$$Np M$"o$ssbauer data of 1 exhibited para magnetic-relaxation spectra similar to other oxo-neptunyls (+1,+2), the DC-$$M$$ data have revealed many strikingly different features of 1 from the latter: first, its reciprocal susceptibility ($$chi$$$$^{-1}$$) vs. $$T$$(K) plots showed a peculiar strongly field ($$H$$)-dependent nonparamagnetic behavior, which suggests the presence of small ferromagnetic component with $$T$$$$_{C}$$$$>$$300 K. In addition, its low-temperature isothermal $$M$$ exhibited anomalous relaxation behavior involving initial over-responsive $$M$$ change and subs equent drift back to its "equilibrium" value ($$M$$$$_{rm eq}$$). Moreover, such $$M$$$$_{rm eq}$$ showed strong perturbation effect from the SQUID-$$M$$ measurement itself. Such novel magnetic features suggest the presence of a largely metastable fluctuating magnetic (spin plus orbital) state in 1 as a collective body of individual Ising-type neptunyl (O=Np=O)$$^{+2}$$ molecular magnets.

Journal Articles

Revaluation of the correlation of isomer shift with Np-O bond length in various neptunyl(V and VI) compounds

Saeki, Masakatsu; Nakada, Masami; Kawasaki, Takeshi*; Nishimura, Tatsuru*; Kitazawa, Takafumi*; Takeda, Masuo*

Journal of Radioanalytical and Nuclear Chemistry, 270(2), p.379 - 384, 2006/11

https://doi.org/10.1007/s10967-006-0360-x
 Times Cited Count：3 Percentile：23.49(Chemistry, Analytical)

no abstracts in English

Journal Articles

Molecular magnetism of neptunyl (+2) complex NpO$$_{2}$$(C$$_{6}$$H$$_{7}$$O$$_{2}$$)$$_{2}$$(C$$_{5}$$H$$_{5}$$N)

Nakamura, Akio; Nakada, Masami; Nakamoto, Tadahiro*; Kitazawa, Takafumi*; Takeda, Masuo*

Journal of the Physical Society of Japan, 75(Suppl.), p.146 - 148, 2006/08

no abstracts in English

Journal Articles

Relationship between M$"o$ssbauer Isomer shifts and Structures of Neptunium compounds

Saeki, Masakatsu; Nakada, Masami; Kitazawa, Takafumi*

KURRI-KR-106, p.38 - 42, 2004/03

no abstracts in English

Journal Articles

A New type of neptunyl(VI) hydroxide which is topologically similar to $$alpha$$-UO$$_{2}$$(OH)$$_{2}$$

Nakada, Masami; Kitazawa, Takafumi*; Saito, Takashi*; Wang, J.*; Takeda, Masuo*; Yamashita, Toshiyuki; Saeki, Masakatsu

Bulletin of the Chemical Society of Japan, 76(7), p.1375 - 1378, 2003/07

https://doi.org/10.1246/bcsj.76.1375
 Times Cited Count：6 Percentile：29.56(Chemistry, Multidisciplinary)

no abstracts in English

Oral presentation

Investigation of the multiorbital Kondo effect in a 5f-electron compound (Lu,U)Ru$$_2$$Zn$$_{20}$$

Kitazawa, Takafumi; Tokunaga, Yo; Haga, Yoshinori; Opletal, P.; Sakai, Hironori; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Kambe, Shinsaku; Ikeda, Yoichi*; Fujita, Masaki*

no journal, , 

Oral presentation

Investigation of the multiorbital Kondo effect in a uranium compound Lu$$_{1-x}$$U$$_x$$Rh$$_2$$Zn$$_{20}$$

Kitazawa, Takafumi; Tokunaga, Yo; Haga, Yoshinori; Opletal, P.; Sakai, Hironori; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Kambe, Shinsaku; Ikeda, Yoichi*; Fujita, Masaki*

no journal, , 

no abstracts in English

Oral presentation

Pulsed high field magnetization measurements in single crystals of the diluted Yb system (Lu, Yb)Rh$$_2$$Zn$$_{20}$$

Kitazawa, Takafumi; Tokunaga, Yo; Haga, Yoshinori; Opletal, P.; Sakai, Hironori; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Kambe, Shinsaku

no journal, , 

no abstracts in English

Oral presentation

Pulsed high magnetic field measurements in a quasi-degenerate diluted Yb system (Lu,Yb)Rh$$_2$$Zn$$_{20}$$

Kitazawa, Takafumi; Ikeda, Yoichi*; Matsuo, Akira*; Imajo, Shusaku*; Shimizu, Yusei*; Kawamata, Masahiro*; Tokunaga, Yo; Haga, Yoshinori; Opletal, P.; Sakai, Hironori; et al.

no journal, , 

A diluted Yb system (Lu,Yb)Rh$$_2$$Zn$$_{20}$$ is an impurity Kondo alloy with quasi-octet degeneracy due to strong $$c$$-$$f$$ hybridization. In addition to the large degeneracy of $$N = 8$$, we found field-induced single-ion magnetic anisotropy above about 5 T, which cannot be explained by the existing Kondo model. To understand the $$f$$-electron state under magnetic fields, where the magnetic anisotropy develops, we measured the magnetization and specific heat of the diluted Yb system (Lu,Yb)Rh$$_2$$Zn$$_{20}$$ under pulsed high magnetic fields. The magnetization curves coincided between the processes of increasing and decreasing magnetic fields. This indicates that eddy-current heating is sufficiently suppressed, and isothermal magnetization curves can be measured. The magnetic easy and hard axes along the $$langle 100 rangle$$ and $$langle 111 rangle$$ directions, respectively, remained unchanged even above the Kondo crossover field of 22.7 T, where the $$f$$-electrons are localized. The field dependence of the electronic specific heat coefficients, estimated from the specific heat measurements, increased to about 1 J Yb-mol$$^{-1}$$ K$$^{-2}$$ and decreased around the Kondo crossover field. The decreasing electronic specific heat coefficients at the Kondo field suggest the localization of the $$f$$-electrons. In addition, the anisotropic magnetic response was observed not only in magnetization but also in specific heat measurements.

Oral presentation

Incommensurate antiferromagnetism in uranium-based van der Waals magnet $$alpha$$-UTe$$_3$$

Sakai, Hironori; Tabata, Chihiro; Kaneko, Koji; Hirose, Yusuke; Kitazawa, Takafumi; Yamamoto, Etsuji; Tokiwa, Yoshifumi; Kambe, Shinsaku; Tokunaga, Yo; Haga, Yoshinori

no journal, , 

In this study, a single crystal of uranium-based van der Waals compound $$alpha$$-UTe$$3$$ was successfully grown. The structure features distinct Te sites, including a Te-Te bilayer, and a corrugated U network with U-U distances significantly exceeding the Hill limit, indicating a localized $$f$$-electron system. The material shows semiconducting in-plane transport and easy-plane magnetic anisotropy. An antiferromagnetic transition occurs at $$T_{rm N}$$ = 5 K, but the magnetic structure was previously unknown. Neutron diffraction was performed to clarify the magnetic order, and this presentation discusses the compound's structural, electronic, and magnetic properties.

Oral presentation

Determination of the hyperfine coupling constant in HoCo$$_2$$Zn$$_{20}$$ via thermodynamic measurements

Kitazawa, Takafumi; Shimura, Yasuyuki*; Onimaru, Takahiro*; Haga, Yoshinori; Sakai, Hironori; Tokiwa, Yoshifumi; Kambe, Shinsaku; Yamamoto, Etsuji; Tokunaga, Yo

no journal, , 

no abstracts in English

Oral presentation

Magnetism in uranium-based van der Waals compound $$alpha$$-UTe$$_3$$

Sakai, Hironori; Tabata, Chihiro; Kaneko, Koji; Kitazawa, Takafumi; Yamamoto, Etsuji; Tokiwa, Yoshifumi; Kambe, Shinsaku; Tokunaga, Yo; Haga, Yoshinori

no journal, , 

In this study, we successfully grew a single crystal of the uranium-based van der Waals compound $$alpha$$-UTe$$_3$$. The crystal structure includes a Te-Te bilayer composed of Te(2) and Te(3) atoms. The U and Te(1) atoms are between the double Te layers. The shortest U-U distance exceeds the Hill limit of $$sim$$3.5 $AA. Therefore, one expects this compound to be regarded as the localized $f$$ electron system. The conduction properties within the $$c$$-plane exhibit semiconducting behavior, and the magnetism demonstrates easy-plane anisotropy. An antiferromagnetic transition occurs at $$T_{rm N}$$ =5 K; however, the magnetic structure remains undetermined. We conducted neutron diffraction experiments to elucidate the magnetic structure and address this. This presentation will discuss this compound's fundamental physical and magnetic properties.

Oral presentation

Magnetism in $$alpha$$-UTe$$_3$$

Sakai, Hironori; Tabata, Chihiro; Kaneko, Koji; Hirose, Yusuke; Kitazawa, Takafumi; Yamamoto, Etsuji; Tokiwa, Yoshifumi; Kambe, Shinsaku; Tokunaga, Yo; Haga, Yoshinori

no journal, , 

We have investigated the magnetic properties of a single crystal of a uranium-based van der Waals compound $$alpha$$-UTe$$_3$$ through the measurements of macroscopic physical properties and neutron scattering experiments. Based on the experimental results, we would like to discuss the magnetic properties of this compound.

Oral presentation

High magnetic field specific heat of a quasi-degenerate Kondo alloy (Lu, Yb)Rh$$_2$$Zn$$_{20}$$

Kitazawa, Takafumi; Ikeda, Yoichi*; Imajo, Shusaku*; Haga, Yoshinori; Kohama, Yoshimitsu*; Tokunaga, Yo; Fujita, Masaki*

no journal, , 

no abstracts in English

Oral presentation

Physical properties of uranium containing Tsai-type approximant

Haga, Yoshinori; Tokiwa, Yoshifumi; Sakai, Hironori; Kitazawa, Takafumi; Yamamoto, Etsuji; Kambe, Shinsaku; Tokunaga, Yo; Muro, Yuji*

no journal, , 

Oral presentation

Crystal structure and low-temperature properties of uranium-containing Tsai-type approximant Al-Au-U

Haga, Yoshinori; Tokiwa, Yoshifumi; Sakai, Hironori; Kitazawa, Takafumi; Yamamoto, Etsuji; Kambe, Shinsaku; Tokunaga, Yo; Ikarugi, Riko; Muro, Yuji*

no journal, , 

no abstracts in English

Oral presentation

Basic physical properties of single crystalline HoTr$$_2$$Zn$$_{20}$$ (Tr = Co, Rh, Ir)

Kitazawa, Takafumi; Haga, Yoshinori; Sakai, Hironori; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Kambe, Shinsaku; Tokunaga, Yo

no journal, , 

no abstracts in English

23 (Records 1-20 displayed on this page)