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Journal Articles

Collapsing processes of charge ordered structure in charge- and spin- frustrated ferrite YbFe $_{2}$ O $_{4}$

Matsumoto, Keisuke*; Koyama, Tsukasa*; Mori, Shigeo*; Yoshii, Kenji; Ikeda, Naoshi*

Journal of Physics; Conference Series, 320, p.012085_1 - 012085_5, 2011/09

https://doi.org/10.1088/1742-6596/320/1/012085

Times Cited Count：0 Percentile：0.00(Physics, Condensed Matter)

In order to clarify the stability of charge ordered structure (CO) in charge- and spinfrustrated ferrite YbFe $_{2}$ O $_{4}$ , we have investigated changes of the CO structure by partial substitution of Mn $^{2+}$ for Fe $^{2+}$ in YbFe $_{2}$ O $_{4}$ by a transmission electron microscope (TEM), incombination with conventional dielectric measurement. It is revealed that subtle substitution of Mn $^{2+}$ for Fe $^{2+}$ in YbFe $_{2}$ O $_{4}$ destroyed drastically the CO structure with the wave vector of q=1/3 1/3 1/2 and, instead, induced polar clustering structure characterized by honeycomb shaped diffuse scatterings in the reciprocal space. The formation of polar clustering structure should be responsible for the characteristic dielectric dispersion.

Journal Articles

X-ray absorption spectra in pyrochlore niobates

Torigoe, Shuhei*; Ishimoto, Yutaro*; Hanasaki, Noriaki*; Nogami, Yoshio*; Matsumura, Daiju; Yoshii, Kenji; Yoneda, Yasuhiro; Nishihata, Yasuo

Journal of Physics; Conference Series, 320, p.012078_1 - 012078_4, 2011/09

https://doi.org/10.1088/1742-6596/320/1/012078

Times Cited Count：1 Percentile：32.53(Physics, Condensed Matter)

The X-ray absorption spectra of some pyrochlore niobates reveal the valence of the Nb ion in each material, and the displacement of the Nb ions from the center of the oxygen octahedra in the pyrochlore niobates YCaNb $_{2}$ O $_{7}$ and NdCaNb $_{2}$ O $_{7}$ , which is consistent with the previous report of the neutron diffraction.

Journal Articles

ToF inelastic neutron scattering studies on quantum spin systems (CuCl)LaO ( = Nb, Ta)

Kawamura, Seiko; Nakajima, Kenji; Inamura, Yasuhiro; Tsujimoto, Yoshihiro*; Kitada, Atsushi*; Takeiri, Fumitaka*; Kageyama, Hiroshi*; Ajiro, Yoshitami*; Nishi, Masakazu*; Kakurai, Kazuhisa

Journal of Physics; Conference Series, 320, p.012037_1 - 012037_5, 2011/09

https://doi.org/10.1088/1742-6596/320/1/012037

Times Cited Count：0 Percentile：0.00(Physics, Condensed Matter)

The magnetic ground state of (CuCl)LaNbO has been suggested to be a spin-singlet state with an excitation gap of meV, while (CuCl)LaTaO has an antiferromagnetic (AFM) ground state. The systems are suspected to be a frustrated quantum spin system due to the competition between the nearest and next-nearest exchange interactions. We have studied magnetic excitation in these systems by ToF inelastic neutron scattering technique. The measurements were performed on powder samples of (CuCl)LaNbO and (CuCl)LaTaO at a disk-chopper-type spectrometer AMATERAS in J-PARC. In both systems, a band-like excitation was observed at meV. The dependence of the intensity of magnetic excitation around 2 meV for (CuCl)LaNbO well reproduces that observed at a triple-axis spectrometer, exhibiting characteristics of spin-singlet dimers. On the other hand, (CuCl)LaTaO in the AFM state exhibits a different dependence.