(The) study of coherent optical and acoustic phonons in correlated electron materials : CMR, multiferroic = 거대자기저항효과 물질과 다강체 물질에서의 결맞음 포논에 대한 연구 CMR, multiferroic

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dc.contributor.advisorAhn, Jae-Wook-
dc.contributor.advisor안재욱-
dc.contributor.authorJang, Kyeong-Jin-
dc.contributor.author장경진-
dc.date.accessioned2011-12-14T07:28:46Z-
dc.date.available2011-12-14T07:28:46Z-
dc.date.issued2010-
dc.identifier.urihttp://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=455322&flag=dissertation-
dc.identifier.urihttp://hdl.handle.net/10203/47652-
dc.description학위논문(박사) - 한국과학기술원 : 물리학과, 2010.08, [ ⅸ, 95 p. ]-
dc.description.abstractThe pump-probe experiment on manganites, which are colossal magnetoresistance materials, $La_{1/4}Pr_{3/8}Ca_{3/8}MnO_3$ and multiferroic materials, $LuMnO_3$ and $YMnO_3$ are carried out. The hole-doped rare-earth manganite, e.g. $La_{1-x}Ca_xMnO_3$, shows colossal agnetoresistance and different temperature-dependent phases. For $0.2<x<0.5$, it displays ferromagnetic metallic behavior at low temperature. For $x>0.5$ it shows charge-ordering phase at low temperature. If substituting Pr for La in $La_{5/8}Ca_{3/8}MnO_3$, the ferromagnetic metallic and charge-ordering phases are coexist at low temperature. For this sample, $La_{1/4}Pr_{3/8}Ca_{3/8}MnO_3$, the coherent optical and acoustic phonons are observed using femtosecond pump-probe spectroscopy. emperature dependent measurements of the time-resolved optical reflectance revealed that the energy of the photoexcited electrons dissipated during relaxation to acoustic phonons, in the high-temperature paramagnetic phase, and to optical phonons, in the low-temperature charge-ordering phase. Analysis of the temperature-dependent behavior reveals that the modal amplitudes of the coherent phonons appear strongly correlated with the charge-ordering phase. Hexagonal multiferroics, $LuMnO_3$ and $YMnO_3$, are different types of rare-earth manganites. These materials have hexagonal structure in $ab$ plane and display phase transitions: a ferroelectric phase transition at high temperature $\sim$900 K, an antiferromagnetic phase transition at 90 K ($LuMnO_3$) or 80 K ($YMnO_3$). These hexagonal rare-earth manganites show multiferroic properties, which coupled electrical(ferroelectricity) and magnetic(antiferromagnetic) properties. In the $LuMnO_3$ thecoherent optical and acoustic phonons are generated above antiferromagnetic phase transition temperature ($T_{\rmN}$), while both couldn`t generated below $T_{\rm N}$. In the $YMnO_3$, the abrupt change of coherent acoustic phonon was measured. These temperature-dependent be...eng
dc.languageeng-
dc.publisher한국과학기술원-
dc.subjectmultiferroic-
dc.subjectLPCMO-
dc.subjectcoherent phonon-
dc.subjectpump-probe-
dc.subject펌프-프로브-
dc.subject자기저항효과물질-
dc.subject다강체-
dc.subject결맞음 포논-
dc.title(The) study of coherent optical and acoustic phonons in correlated electron materials : CMR, multiferroic = 거대자기저항효과 물질과 다강체 물질에서의 결맞음 포논에 대한 연구-
dc.title.alternativeCMR, multiferroic-
dc.typeThesis(Ph.D)-
dc.identifier.CNRN455322/325007 -
dc.description.department한국과학기술원 : 물리학과, -
dc.identifier.uid020037546-
dc.contributor.localauthorJang, Kyeong-Jin-
dc.contributor.localauthor장경진-
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