Magnetoelectric Effects in Ferromagnetic Oxides with the Double Perovskite Structure
| Project/Area Number |
18540342
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Condensed matter physics II
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| Research Institution | The University of Electro-Communications |
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Principal Investigator |
ASAI Kichizo The University of Electro-Communications, Faculty of Electro-Communications, Professor (00109795)
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| Co-Investigator(Kenkyū-buntansha) |
ABE Kohji The University of Electro-Communications, Faculty of Electro-Communications, Professor (20183139)
KOBAYASHI Yoshihiko The University of Electro-Communications, Faculty of Electro-Communications, Research Associate (60293122)
SATO Keisuke FUJITSU Laboratories Ltd, Device & Materials Laboratories, Research (10418212)
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| Project Period (FY) |
2006 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥3,830,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥330,000)
Fiscal Year 2007: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2006: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Keywords | Ferromagnetic & ferroelectric material / Multiferroic / Magnetoelectric effect / Double perovskite structure / Superexchange interaction / Hyperfine magnetic field / NMR / Maxwell-Wagner model / 強磁性強誘電体 / <55>^Mn NMR |
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| Research Abstract |
We have investigated (1) the crystal structure and the magnetic-dielectric properties, (2) competition of the ferromagnetism and ferroelectricity, and (3) the magnetoelectric effects of La_<1-x>Bi_xMn_<0.5>Ni_<0.5>O_3 by means of the x-ray diffraction, magnetic and electric measurements, and ^<55>Mn NMR.
(1) Polycrystalline La_<1-x>Bi_xMn_<0.5>Ni_<0.5>O_3 with the double perovskite structure has been successfully synthesized for x=0〜0.9 by soft chemical synthesis at ambient pressure. The dielectric constant increases and the ferromagnetic Curie temperature (T_<CM>) decreases with increasing x.
(2) It has been clarified through NMR of ^<55>Mn in REMn_<0.5>(Ni_<1-x>Mg_x)_<0.5>Ni_<0.5>O_3 (RE = rare earth elements) that the covalency parameter, f(RE), for Mn^<4+>-O^<2->-Ni^<2+> bond in the double perovskite is evaluated from the hyperfine magnetic field, H_<HF>, at ^<55>Mn. Based on the knowledge, the covalency parameter, f (x), for the bond in La_<1-x>Bi_xMn_<0.5>Ni_<0.5>Ni_<0.5>O_3 is fou
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nd to decrease with increasing x by ^<55>Mn NMR study of the oxides. The decrease of T_<CM> with increasing xis naturally explained with the decrease of f(x).
The decrease of f (x) is attributed to the strong covalency of Bi^<3+>-O^<2-> bond compared with La^<3+>-O^<2-> bond; more electrons of O^<2-> ions are attracted to and populate in Bi^<3+>-O^<2-> bond resulting in deficiency of electrons in Mn^<4+>-O^<2->-Ni^<2+> bond. The ferroelectricity arising from the covalency of Bi^<3+>-O^<2-> bond and the ferromagnetism arising from that of Mn^<4+>-O^<2->-Ni^<2+> bond compete with each other through the competition of the covalencies of both bonds.
(3) For x≧0.5, the dielectric constant increases in a magnetic field near T_<CM>. For x=0.7, the increment of the dielectric constant amounts to 7% at T_<CM> in 9 T. The temperature and the magnetic field dependence of the dielectric constant, including the frequency dispersion, has interpreted based on the Maxwell-Wagner model assuming an inhomogeneity of the sample which contains domains with relatively high dielectric constant dispersed in the material with negative magneto-resistance. Less
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Report
(3 results)
Research Products
(21 results)
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[Presentation] ^55Mn NMR in La<1-x>Bi_xMn<0.5>Ni<0.5>O_32007
Author(s)
T. Kawakami, S. Enoshita, M. Kamogawa, M. Shiozawa, Y. Kobayashi, K. Asai
Organizer
The 62nd Annual Meeting of the Physical Society of Japan
Place of Presentation
Sapporo
Year and Date
2007-09-22
Description
「研究成果報告書概要(欧文)」より
Related Report
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