2014/06/30 by Hiroshi Takatsu, Kunihiko Watanabe, Kazuki Goto +1
Chemistry · Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Antiferromagnetism #Chemistry #Condensed matter physics #Crystal structure #Crystallography #Materials science #Neutron diffraction #Nuclear materials and radiation effects #Order (exchange) #Phase (matter) #Physics #Pyrochlore #Superlattice #Topological Materials and Phenomena #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.90.235110
published as Phys. Rev. B 90, 235110 (2014) · 6 pages, 4 figures
openalex publication_date 2014/12/04 · arxiv created 2014/12/11 · arxiv updated 2014/12/12 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The cubic symmetry of pyrochlore iridium oxides R2Ir2O7 (R=Nd, Eu, and Pr) has been investigated by high resolution x-ray diffraction experiments down to 4 K, in order to clarify the relationship between the metal-insulator transition (MIT) and the small structural phase transition suggested by Raman scattering experiments in these compounds. We have found that a small negative thermal expansion of the order of 10^\ensuremath-3 \AA appears only in Nd2Ir2O7 below the MIT, TMIT=34 K, ascribable to the magnetovolume effect of the long-range order of Ir moments. However, any breaking of the cubic symmetry of three iridates has not been observed as appearance of superlattice reflections nor splittings of cubic reflections below TMIT. These results imply that lowering of the cubic symmetry plays a minor role for the change in the electronic state of these compounds, while a magnetic order of Ir moments plays a major role for the MIT.