| Research Abstract |
This study was carried out to elucidate the mechanism of the evolution of functions in the perovskite type oxides by means of isotope exchange method. Following materials were selected for the investigations. (1) Ferromagnetic materials caused by double exchange, (2) Lithium ion super ion conductor (3) Quantum para and ferro electric materials. The results are summarized as follows.
(a) Effect of oxygen isotope exchange in double exchange system.
Ferromagnetism caused by double exchange and antiferromagnetism caused by charge ordering were investigated. TィイD2cィエD2 and TィイD2NィエD2 were found to decrease and increase, respectively, and the values of the changes were quite large compared to those based on the conventional theory.
(b) Effect of oxygen and Lithium isotope exchange in the Lithium superior conductors.
Exchanges of Lithium and oxygen isotopes were carried out for (La, Li)TiOィイD23ィエD2. The former changed the activation energy for the Lithium ion but the latter did the pre-exponential term. The detail was discussed based on the quantum theory.
(c) Effect of oxygen isotope exchange in the dielectric materials.
Oxygen isotope exchange for the quantum paraelectric SrTiOィイD23ィエD2 conducted a change to ferroelectric state. The mechanism was investigated by the Raman Spectroscopy, Brillouin scattering, and D-E loop, and pryoelectricity measurements.
Role of optical and acoustic phonons in the evolution of ferroelectricity was elucidated.
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