1998 Fiscal Year Final Research Report Summary
Phonon Scattering Mechanisms near Mott Transition in Highly Correlated Electron Systems
| Project/Area Number |
09640414
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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 |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | IWATE UNIVERSITY |
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Principal Investigator |
IKEBE Manabu IWATE UNIV.Facul.Eng.Professor, 工学部, 教授 (40005955)
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| Co-Investigator(Kenkyū-buntansha) |
FUJISHIRO Hiroyuki IWATE UNIV.Facul.Eng.Associate Prof., 工学部, 助教授 (90199315)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Manganese Oxides / Thermal Conductivity / Thermal Diffusivity / Sound Velocity / Phonon Scattering / Ferromagnetic Transition Interaction / Charge-Ordering Transition |
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| Research Abstract |
As recent revived studies on perovskite-based manganites have confirmed, R_<1-X>A_XMnOTAU23EPSILON2-type crystals undergo a variety of phase transitions which originate from the interplay and competition of various physical interactions. There are many results of electric, magnetic and crystallographic properties in these manganites, however, the thermal (phonon) transport properties such as the thermal conductivity kappa, thermal diffusivity alpha, sound velocity upsilon_S and thermal dilatation dL/L have not been reported. In this study, we measured these thermal transport properties of La Sr Mn 03 (LSMO) crystals (0.1 <X<0.9) and investigated the phonon scattering mechanisms near the ferromagnetic transition temperature T_C and the change ordering temperature T_<CO2>.
The remarkable results are as follows ;
(1)The sound velocity upsilon_S anomaly has been observed which is related to the polaron-ordering temperature T_P centered at X=1/8. The upsilon_S is the powerful measure to detect the charge ordering.
(2)The thermal conductivity kappa of LSMO (X=O.1 7 and 0.155) is markedly reduced over a wide temperature range near the ferromagnetic transition temperature T0. The analyses of 1 have revealed the existence anomalously strong phonon scattering.
(3)We confirmed the magnetic phase transition from a ferromagnetic insulator to an antiferromagnetic insulator in LSMO polycrystals at around X=O.50 for the first time.
(4)The anomalies of the sound velocity upsilon_S and thermal dilatation dLIL of LSMO system (0.48<X<0.90) strongly suggest the occurrence of the charge ordering.
(5)A phase diagram of the charge-ordered state in La_<1-X>Sr_XMnO_3 as a function of temperature T and the Sr concentration X is proposed.
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