Research Project
Grant-in-Aid for Scientific Research (B)
We made a research for triangular mixed valence material RFe2O4 which exhibits a polar charge ordering from the frustrated charge interaction. In this two years we had built up an air tight furnace having sample weight measurement system. From the detailed information of the sample weight change during the various heat treatment, we developed couple of method in obtaining fine sample of RFe2O4. During the course of the research we found the various electronic phases and properties for YbFe2O4, RFeCoO4, RFeCuO4 and RGaCuO4 (R.= Yb, Lu)Recently the ferroelectricity arise from the polar ordering of electrons have got much attention, however the usability for the actual application on the ferroelectric material have still been an open question. For example high electronic conductivity that possibly exist in the correlated electron system may prevent the usual application for the ferroelectrics like as insulator, charge condenser and so on. This report is one of the possibility search for s … More uch quests. For example in some sample treatment condition can possibly realize a high resistivity states of electronic ferroelectrics. It is also interesting that the sample having less oxygen vacancy shows high activation energy than non-stoichiometric material. It has been explained that the origin of the dielectric dispersion for Rfe_2O_4 is the boundary motion for polar domains. The higher Q value for higher stoichiometric sample indicates that the less oxygen vacant sample has larger charge ordering coherence length. Which realizes lamer scale of the collective electron motion.We emphasize that such ferroelectricity, defined by the electron distribution, is crucially different from previously known ferroelectrics. The difference in the origin of ferroelectricity may enable the development of a new class of device application in the near future. For example an anomaly report exists in electron microscope observation, which revealed an extremely small ferroelectric domain having a coherent size of 10 nm scale. This is a consistent estimate from the X-ray diffraction experiments. The superlattice profile is wider than the fundamental Bragg spot. Using the Schemer's formula the coherence length was estimated as about 10 nm from the full width of the half maximum of the peak profile in the a-b plane. In this ferroelectric the Coulomb interactions between Fe^<3+> and Fe^<2+> dominate the total energy for the presence of the domain sizes, that is decoupled from the lattice distortion. This indicates a typical property of the ferroelectricity by ordered electrons, free of lattice distortion. Future study may reveal such an extremely small ferroelectric element in high density electric devices in such extremely small domains.The applicability of electronic ferroelectric material for conventional ferroelectrics is still an open question. We should continue to find out better method to realize high stoichiometric RFe_2O_4, or also we should find out more characteristic application that may suit for such material having electric polarization and good conductivity. Less
All 2008 2007 2006 Other
All Journal Article (101 results) (of which Peer Reviewed: 46 results) Presentation (63 results) Patent(Industrial Property Rights) (2 results)
Phys. Rev. B 77
Pages: 115128-6
機能材料 28
Pages: 76-84
日本放射光学会誌 21
Pages: 20-24
10019913798
Pages: 87-96
Phys., Rev B 77
KINOU ZAIRYOU 28
Jpn. J. Synch. Rad., Soc 21
Jpn. J. Synch. Rad. Soc 21
Ferroelectrics 348
Pages: 38-47
J. Mag. Mag. Mat. 310
Pages: 1154-1156
Pages: 793-795
Jpn. J. Appl. Phys. 46
Pages: 7171-7174
Phys. Rev. B 76
Pages: 24423-12
Pages: 94113-10
J. Korean Phys. Soc. 51
Pages: 821-831
Ferroelectrics 346
Pages: 162-167
130004661636
J. Solid State Chem. 181
Pages: 377-381
Trans. Mater. Res. Soc. Jpn. 32[1]
Pages: 51-54
J. Mag. Mag. Mater 310
Pages: 1070-1072
Pages: 184441-5
Mater. Res. Symp. Proc. 966
Journal of the Korean Physical Society 51
Pages: 828-831
J. Mag. Mag. Mater. 310
Pages: 870-872
Pages: 782-784
Appl. Phys. Lett. 90
Pages: 133123-3
Pages: 170-176
Pages: 33-37
Ferroelectrics 355
Pages: 119-124
130004661570
J. Mag. Mag. Mat 310
Pages: 349-351
Jpn. J. Appl. Phys 46
Phys Rev B 76
Phys. Rev B 76
Phys. Soc 51
J. Solid State Chem 181
Oxides R2MRuO6 (R=La, Pr and Nd, M=Mg, Co, Ni and Zn Trans., Mater., Res., Soc., Jpn 32(1)
Focus on Solid State Chemistry (Ed., by Arte M., Newman)
Pages: 63-75
Mater. Res. Symp. Proc 966
Appl. Phys. Lett 90
J.Magn.Magn.Mat 310
Pages: 1154-1154
Physica B 378-380
Pages: 548-549
Phys. Stat. Sol. (c) 3
Pages: 2762-2766
J. Phys.: Conf. Ser. 51
Pages: 498-501
Materials Research Society Symposium Proceedings 966
Pages: 210-216
Physica B 385-386
Pages: 119-122
Appl. Phys. Lett. 89
Pages: 233120-3
Phys. Rev. Lett 96
Pages: 86406-4
J. Phys. Soc. Jpn 75
Pages: 94706-5
Physica B 378-80
Pages: 585-586
Phys. Stat. Sol. (a) 203
Pages: 2812-2817
J. Am. Chem. Soc. 128
Pages: 6676-6682
Phys. Stat. Sol (c) 3
J. Phys. : Conf. Ser 51
Materials Research Society Symposium Proceedings 96
J. Appl. Phys 99
Phys., Rev., Lett 96
J. Am. Chem. Soc 128
Phys.Rev.Lett 96
Pages: 86406-86406
J.Phys.Soc.Jpn 75
Pages: 94706-94706
Pages: 585-585
Phys.Stat.Sol.(a) 203
Pages: 2812-2812
J.Am.Chem.Soc. 128
Pages: 6676-6676
Focus on Solid State Chemistry (Ed. by Arte M. Newman), 2007
MRS Symposium proceedings (in press)
Ferroelectrics (in press)
J.Korean Phys.Soc (in press)
J.Korean Phys.Soc. (in press)
J.Magn.Magn.Mat. (in press)
Topology in Ordered Phase (in press)