Comparative study of optical phonons in the rhombohedrally distorted perovskites<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">LaAlO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">LaMnO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow><

Abrashev, M. V.; Litvinchuk, A. P.; Iliev, M. N.; Meng, R. L.; Popov, V. N.; Ivanov, V. G.; Chakalov, R. A.; Thomsen, C.

doi:10.1103/physrevb.59.4146

Cited by 300 publications

(230 citation statements)

References 30 publications

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“…4. LaCoO 3 : The spectra of LaCoO 3 are, however, somewhat surprising since (i) they are not similar to the spectra of isostructural rhombohedral LaMnO 3+d [9,10,21,22], La 1-x A x MnO 3 [9,10], and LaAlO 3 [22], (ii) due to the neutron-diffraction data the sample should have a rhombohedral symmetry D d . Note that high-frequency lines, with large intensity in LaCoO 3 even at room temperature, are not observed in the spectra of isostructural compounds.…”

Section: Vp Gnezdilov Et Almentioning

confidence: 96%

Phonon Raman scattering in LaMn1−xCoxO3 (x=0, 0.2, 0.3, 0.4, and 1.0)

Gnezdilov

Yeremenko

Pashkevich³

et al. 2003

Low Temperature Physics

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The Raman-active phonons in perovskite-like LaMn 1-x Co x O 3 (x = 0, 0.2, 0.3, 0.4, and 1.0) were studied by measuring Raman spectra at temperatures of 295 and 5 K. The changes in the spectra with Co doping are correlated with the decrease of orthorhombic distortions. Surprisingly more phonon lines than allowed for the rhombohedral LaCoO 3 structure were observed. The manganese perovskites of the type R 1-x A x MnO 3 (R = rare earth, A = Ca, Sr, Ba, or Pb) have been subject of scientific investigations for many decades. Recently, this interest has been renewed due to the observation of a colossal magnetoresistance [1,2], charge, spin, and orbital ordering effects as a function of Mn 3+ /Mn 4+ ratio [3][4][5]. Another system, Mn-site-doped, with the composition LaMn 1-x D x O 3 (D = Cr, Fe, Co, or Ni) was intensively studied in the 60's, but colossal magnetoresistance was not mentioned in them until the 90's [6]. While Raman spectra of La-site-doped compounds have been reported in numerous of publications [7][8][9][10][11][12][13], surprisingly nothing was done on Mn-site-doped compounds. In this work we report the results of an optical phonon study in the perovskite oxides LaMn 1-x Co x O 3 (x = 0, 0.2, 0.3, 0.4, and 1.0). The end member of this system, namely LaCoO 3 has been the subject of continuing interest since the 50's due to unusual magnetic properties and two spin-state transitions [14,15].

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Section: Vp Gnezdilov Et Almentioning

confidence: 96%

Phonon Raman scattering in LaMn1−xCoxO3 (x=0, 0.2, 0.3, 0.4, and 1.0)

Gnezdilov

Yeremenko

Pashkevich³

et al. 2003

Low Temperature Physics

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“…However, no sharp peaks appear when the sample enters FM state in the film on STO. In addition, because the E g modes always appear in rhombohedral symmetric structure 43,47 , the appearance of these sharp peaks maybe indicate a structure transition from orthorhombic lattice to rhombohedron. These sharp peaks in the 400 to 450 cm −1 range at low temperatures also appears in bulk samples with composition of about 0.33 41 .…”

Section: A Effect Of Temperaturementioning

confidence: 99%

Raman spectra in epitaxial thin films ofLa1−xCaxMnO3(
Xiong
¹
,
Chen
²
,
Wang
³

et al. 2004
Phys. Rev. B
50
2
23
2
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Raman spectra of LCMO films grown on LAO (001), STO (001), and MgO (001) substrates were studied at different temperatures. The effect of temperature, doping level and strain on Raman spectra are discussed in detail. With decreasing temperature, the changes of Raman spectra are correlated with the disorder-order transition, shuch as: paramagnetism to ferromagnetism, and chargeordering. The strain induced by lattice-substrate mismatch affects the Raman spectra strongly. The mode induced by disorder of oxygen defects is apparently observed in La0.67Ca0.33M nO3 film on STO due to the larger tensile strain. While this mode can not be seen in the Raman spectra for the films on LAO and MgO. A strong unsigned mode at about 690 cm −1 is observed in all films except for La0.67Ca0.33M nO3 film on LAO, which is not observed in bulk sample easily. It suggests that the mode is closely related to the strain.

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“…a film = a substrate b film = b substrate This constraint is quite strong since it is associated with bond elongation, i.e. the most energetic vibrational modes 11 . It thus relaxes slowly (not before 250 u.c., 1000Å, on a STO substrate 5 ).…”

mentioning

confidence: 99%

Interface Effects in Perovskite Thin Films

2012

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The control of matter properties (transport, magnetic, dielectric,. . . ) using synthesis as thin films is strongly hindered by the lack of reliable theories, able to guide the design of new systems, through the understanding of the interface effects and of the way the substrate constraints are imposed to the material. The present paper analyses the energetic contributions at the interfaces, and proposes a model describing the microscopic mechanisms governing the interactions at an epitaxial interface between a manganite and another transition metal oxide in perovskite structure (as for instance SrTiO3). The model is checked against experimental results and literature analysis.The technological importance of spin valves or spin injectors as potential applications of manganese oxides induced a large number of works on manganite thin films 2,3 . For this reason the lost of magnetization of La 2/3 Sr 1/3 MnO 3 (LSMO) or La 2/3 Ca 1/3 MnO 3 (LCMO) near an SrTiO 3 (STO) interface has been the subject of many interpretations. Let us cite (i) homogeneous substrate strain 4 (ii) electronic and/or chemical phase separation 5 related to structural inhomogeneities at the interface 6 , (iii) manganese e g orbital reconstruction inducing C-type antiferromagnetism 7,8 . None of these interpretations however provide a good understanding of the observed phenomena. For instance, it was shown that an homogeneous substrate strain of the in-plane parameters does not relax for film thickness smaller than 1000Å 5 , while a drastic change in the transport properties is observed for films thinner than a few unit cells (∼ 3 − 4 on STO substrate 7,9 , ∼ 30 on LaAlO 3 substrate 7 ,. . . ). In the second hypothesis (ii), there is no clear proposition of the nature of the inhomogeneities, their origin, the way they may act in order to induce the observed properties. Finally, ferromagnetic hysteresis loops were found in very thin films up to only three unit cells 9 (u.c.), in contradiction with the proposed C-type AFM ordering resulting from orbital ordering (iii). In any case, whatever the reasons put forward, the existence of a so-called "dead layer" at the interface between the manganite film and most perovskite substrates seems to be established 9,10 . This "dead layer" is of a few unit cells width and exhibits a large decrease of the conductivity ; however its origin is not at all understood.We believe that a careful analysis allow us to infer a model for the interface effects between a manganite and an oxide substrate with a perovskite structure. The main concepts of our model can be summarized as an energy balance at the interface.• It is well known that the strongest effect of the substrate is to constrain the film inplane cell parameters to fit the substrate ones. a film = a substrate b film = b substrate This constraint is quite strong since it is associated with bond elongation, i.e. the most energetic vibrational modes 11 . It thus relaxes slowly (not before 250 u.c., 1000Å, on a STO substrate 5 ). In the literature, it is associ...

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Comparative study of optical phonons in the rhombohedrally distorted perovskitesLaAlO3andLaMnO3<

Cited by 300 publications

References 30 publications

Phonon Raman scattering in LaMn1−xCoxO3 (x=0, 0.2, 0.3, 0.4, and 1.0)

Phonon Raman scattering in LaMn1−xCoxO3 (x=0, 0.2, 0.3, 0.4, and 1.0)

Raman spectra in epitaxial thin films ofLa1−xCaxMnO3(
Xiong
¹
,
Chen
²
,
Wang
³

et al. 2004
Phys. Rev. B
50
2
23
2
View full text Add to dashboard Cite

Interface Effects in Perovskite Thin Films

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Comparative study of optical phonons in the rhombohedrally distorted perovskitesLaAlO3andLaMnO3<

Cited by 300 publications

References 30 publications

Phonon Raman scattering in LaMn1−xCoxO3 (x=0, 0.2, 0.3, 0.4, and 1.0)

Phonon Raman scattering in LaMn1−xCoxO3 (x=0, 0.2, 0.3, 0.4, and 1.0)

Raman spectra in epitaxial thin films ofLa1−xCaxMnO3(Xiong1, Chen2, Wang3 et al. 2004Phys. Rev. B502232View full textAdd to dashboardCite

Interface Effects in Perovskite Thin Films

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Resources

About

Raman spectra in epitaxial thin films ofLa1−xCaxMnO3(
Xiong
¹
,
Chen
²
,
Wang
³

et al. 2004
Phys. Rev. B
50
2
23
2
View full text Add to dashboard Cite