Browsing by Author "Kaneko, Y."

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Orbital ordering of layered manganites from resonant soft X-ray scattering
(2007-03-01)
Chao, K. S.
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Huang, D. J.
;
Okamoto, J.
;
Lin, H.-J.
;
Hsu, C.-H.
We present measurements of Mn L-edge resonant soft X-ray scattering on single-layered manganites with different sizes of cations. Orbital ordering of Pr0.5Ca1.5MnO4 exhibits a stronger three-dimensional character and a dramatically enhanced transition temperature, as compared with those of La0.5Sr1.5MnO4. The c-axis correlation length of orbital ordering in Pr0.5Ca1.5MnO4 is about half of the inplane correlation length. Our results indicate that reduction in one-electron bandwidth and quenched disorder strongly enhances the stabilization of charge-orbital ordering. (c) 2006 Published by Elsevier B. V.
Photocreating supercooled spiral-spin states in a multiferroic manganite
(2016-08-18)
Sheu, Y. M.
;
Ogawa, N.
;
Kaneko, Y.
;
Tokura, Y.
;
電子物理學系
We demonstrate that the dynamics of the ab-spiral-spin order in a magnetoelectric multiferroic Eu0.55Y0.45MnO3 can be unambiguously probed through optical second harmonic signals, generated via spin-induced ferroelectric polarization. In the case of weak excitation, the ferroelectric and the spiral-spin order remains interlocked, both relaxing through spin-lattice relaxation in the nonequilibrium state. When the additional optical pulse illuminating the sample is intense enough to induce a local phase transition thermally, the system creates ametastable state of the bc-spiral-spin order (with the electric polarization P parallel to c) via supercooling across the first-order phase transition between the ab and bc spiral. The supercooled state of the bc-spiral spin is formed in the thermodynamical ground state of the ab spiral (P parallel to a), displaying a prolonged lifetime with strong dependence on the magnetic field along the a axis. The observed phenomena provide a different paradigm for photoswitching between the two distinct multiferroic states, motivating further research into a direct observation of the photocreated supercooled bc-spiral spin in multiferroic manganites.