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SUMMARY:High pressure synthesis of novel perovskite-type oxides with unusu
 ally high valence Co(IV) and Cu(III) ions - Shintaro Ishiwata\, University
  of Tokyo.
DTSTART:20170322T111500Z
DTEND:20170322T121500Z
UID:TALK68882@talks.cam.ac.uk
CONTACT:Helen Verrechia
DESCRIPTION:Perovskite oxides with unusually high valence 3d transition me
 tal ions such as Fe4+ and Co4+ show unique magnetism inherent to the stron
 g p-d hybridization. This is exemplified by the nontrivial helimagnetism a
 nd ferromagnetism in Rh-doped SrFeO3 [1] and room-temperature ferromagneti
 sm in SrCoO3. However\, the search for novel electronic phases in these ox
 ides has been hampered by the difficulty in the sample preparation at high
  pressures.\n In this seminar\, after the brief review on structure and ph
 ysical properties of unusually high valence perovskite-type oxides\, we sh
 ow our recent studies on novel perovskites Sr1-xBaxCoO3 and La1-xPrxCuO3 p
 repared at high pressures. Sr1-xBaxCoO3 shows a novel helimagnetic phase u
 pon the suppression of the ferromagnetic phase by the Ba doping [2]\, and 
 the helimagnetic compound is found to show a giant magnetovolume effect. A
 s for La1-xPrxCuO3\, we found that the compounds with x larger than 0.6 ha
 ve highly distorted GdFeO3-type structure containing quasi-one-dimensional
  Cu-O chains [3]. From the structural and electronic studies combined with
  first-principles calculations\, the oxidation state of Cu in PrCuO3 is fo
 und to be close to 2+ rather than 3+. The novel structural and electronic 
 states of these perovskites with unusually high valence Co4+ and Cu3+ ions
  will be discussed in terms of the interplay between charge\, orbital\, an
 d lattice in oxides with strong p-d and p-d-f hybridizations.\n\n[1] M. Ki
 noshita\, H. Sakai\, N. Hayashi\, Y. Tokura\, M. Takano\, and S. Ishiwata\
 , Angew. Chem. Int. Ed.\, 55\, 15292 (2016).\n[2] H. Sakai et al.\, in pre
 paration.\n[3] M. Ito et al.\, in preparation.\n
LOCATION:Mott Seminar Room (531)\, Cavendish Laboratory\, Department of Ph
 ysics
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