Synchrotron x-ray-diffraction study of orbital ordering in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">YVO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Noguchi, M.; Nakazawa, Atsushi; Oka, Sachiko; Arima, T.; Wakabayashi, Yusuke; Nakao, Hironori; Murakami, Youichi

doi:10.1103/physrevb.62.r9271

Cited by 111 publications

(102 citation statements)

References 20 publications

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“…In the orthorhombic 77 K phase, the empty orbital at site 1, |3 1 , only roughly equals |xz . Our results are consistent with resonant x-ray scattering [5] and magnetization [1] data. LDA+U [6] yields results close to ours [31].…”

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confidence: 91%

Orbital Fluctuations in the Different Phases ofLaVO3andYVO3

2007

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We investigate the importance of quantum orbital fluctuations in the orthorhombic and monoclinic phases of the Mott insulators LaVO3 and YVO3. First, we construct ab-initio material-specific t2g Hubbard models. Then, by using dynamical mean-field theory, we calculate the spectral matrix as a function of temperature. Our Hubbard bands and Mott gaps are in very good agreement with spectroscopy. We show that in orthorhombic LaVO3, quantum orbital fluctuations are strong and that they are suppressed only in the monoclinic 140 K phase. In YVO3 the suppression happens already at 300 K. We show that Jahn-Teller and GdFeO3-type distortions are both crucial in determining the type of orbital and magnetic order in the low temperature phases. The Mott insulating t 2 2g perovskites LaVO 3 and YVO 3 exhibit an unusual series of structural and magnetic phase transitions ( Fig. 1) with temperature-induced magnetization reversal phenomena [1] and other exotic properties [2,3]. While it is now recognized that the V-t 2g orbital degrees of freedom and the strong Coulomb repulsion are the key ingredients, it is still controversial whether classical (orbital order) [1,4,5,6,7,8] or quantum (orbital fluctuations) [2, 9] effects are responsible for the rich physics of these vanadates.At 300 K, LaVO 3 and YVO 3 are orthorhombic paramagnetic Mott insulators. Their structure (Fig. 2) can be derived from the cubic perovskite ABO 3 , with A=La,Y and B=V, by tilting the VO 6 octahedra in alternating directions around the b-axis and rotating them around the c-axis. This GdFeO 3 -type distortion is driven by AO covalency which pulls a given O atom closer to one of its four nearest A-neighbors [10,11]. Since the Y 4d level is closer to the O 2p level than the La 5d level, the AO covalency increases when going from LaVO 3 to YVO 3 and, hence, the shortest AO distance decreases from being 14 to being 20 % shorter than the average, while the angle of tilt increases from 12 to 18 0 , and that of rotation from 7 to 13 0 [12,13]. Finally, the A-cube is deformed such that one or two of the ABA body-diagonals is smaller than the average by, respectively, 4 and 10 % in LaVO 3 and YVO 3 . These 300 K structures are determined mainly by the strong covalent interactions between O 2p and the empty B e g and A d orbitals, hardly by the weak interactions involving B t 2g orbitals, and are thus very similar to the structures of the t 1 2g La and Y titanates [10,11].

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confidence: 91%

Orbital Fluctuations in the Different Phases ofLaVO3andYVO3

2007

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“…Next, the energy dependence of the RXS intensity at (1 0 0) was examined to elucidate the C-OO phase, as shown in figure (b). The energy spectrum drastically changed at the G-OO-C-OO transition, as reported by Noguchi et al, (2000), while there was no change at the G-OO-orbital disorder transition. The signal at 40 K strongly reflects the orbital ordering in the C-OO phase, while RXS at 100 and 250 K reflects the local crystal symmetry.…”

Section: Resultssupporting

confidence: 65%

“…The other phase is G-type orbital order (G-OO), with an antiferroic arrangement in all the three orthogonal directions. These orbital orderings have been studied by RXS (Noguchi et al, 2000). However, there are some unclear points relating to the interpretation of the observed RXS.…”

Section: Introductionmentioning

confidence: 99%

Resonant X-ray scattering study of perovskite-type vanadate RVO₃

et al. 2010

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The orbital ordering in perovskite-type vanadium oxides, RVO 3 (R: rare earth), has been investigated by resonant X-ray scattering (RXS) near the V K-edge energy. The G-type orbital order, C-type orbital order and orbital disorder phases are elucidated on the basis of the azimuthal-angle and polarization dependence of the RXS signal reflecting the orbital ordering. IntroductionResonant X-ray scattering (RXS) is becoming one of the most powerful tools for studying orbital states in strongly correlated electron systems. Therefore, it is important to understand the origin of RXS signals to determine orbital states; the RXS signal reflects not only the orbital state, but also the structural characteristics (Nakao et al., 2006, and references therein). In RVO 3 , the two valence electrons of V 3+ ions occupy the nearly triply degenerate t 2g orbitals. Hence, the physical properties of RVO 3 are coupled with the orbital and spin states. Two types of orbital orderings have been reported in RVO 3 systems. One is C-type orbital order (C-OO), with an antiferroic arrangement of d xy d yz and d xy d zx in the ab plane and a ferroic arrangement along the c-axis. The other phase is G-type orbital order (G-OO), with an antiferroic arrangement in all the three orthogonal directions. These orbital orderings have been studied by RXS (Noguchi et al., 2000). However, there are some unclear points relating to the interpretation of the observed RXS. In this study, we have systematically investigated RXS near the V K-edge energy on the basis of model calculations and have revaluated the orbital orderings in RVO 3 .

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“…I σ−σ ′ (0kℓ) and I σ−π ′ (0kℓ) are proportional to each other as a function of the x-ray energy but differ in their azimuthal symmetries, the σ − σ ′ channel being four-fold symmetric in ψ while the σ − π ′ channel has no particular symmetry. All of these characteristics have been observed in perovskite oxides of this space group [27,36,37]. An incident π component can also give a contribution to the π ′ -polarized scattering.…”

Section: A High Temperature Phase (T > Tcoo)mentioning

confidence: 83%

Resonant x-ray diffraction of the magnetoresistant perovskitePr0.6Ca0.4MnO
Grenier
¹
,
Hill
²
,
Gibbs
³

et al. 2004
Phys. Rev. B
102
5
71
1
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We report a resonant x-ray diffraction study of the magnetoresistant perovskite Pr0.6Ca0.4MnO3. We discuss the spectra measured above and below the semiconductor-insulator transition temperature with aid of a detailed formal analysis of the energy and polarization dependences of the structure factors and ab initio calculations of the spectra. In the low temperature insulating phase, we find that inequivalent Mn atoms order in a CE-type pattern and that the crystallographic structure of La0.5Ca0.5MnO3, (Radaelli et al., Phys. Rev. B 55, 3015 (1997)) can also describe this system in fine details. Instead, the alternative structure proposed for the so-called Zener polaron model (Daoud-Aladine et al., Phys. Rev. Lett. 89, 097205 (2002)) is ruled out by crystallographic and spectroscopic evidences. Our analysis supports a model involving orbital ordering. However, we confirm that there is no direct evidence of charge disproportionation in the Mn K-edge resonant spectra. Therefore, we consider a CE-type model in which there are two Mn sublattices, each with partial eg occupancy. One sublattice consists of Mn atoms with the 3x 2 − r 2 or 3y 2 − r 2 orbitals partially occupied in a alternating pattern, the other sublattice with the x 2 − y 2 orbital partially occupied.

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Synchrotron x-ray-diffraction study of orbital ordering inYVO3

Cited by 111 publications

References 20 publications

Orbital Fluctuations in the Different Phases ofLaVO3andYVO3

Orbital Fluctuations in the Different Phases ofLaVO3andYVO3

Resonant X-ray scattering study of perovskite-type vanadate RVO₃

Resonant x-ray diffraction of the magnetoresistant perovskitePr0.6Ca0.4MnO
Grenier
¹
,
Hill
²
,
Gibbs
³

et al. 2004
Phys. Rev. B
102
5
71
1
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Synchrotron x-ray-diffraction study of orbital ordering inYVO3

Cited by 111 publications

References 20 publications

Orbital Fluctuations in the Different Phases ofLaVO3andYVO3

Orbital Fluctuations in the Different Phases ofLaVO3andYVO3

Resonant X-ray scattering study of perovskite-type vanadate RVO3

Resonant x-ray diffraction of the magnetoresistant perovskitePr0.6Ca0.4MnOGrenier1, Hill2, Gibbs3 et al. 2004Phys. Rev. B1025711View full textAdd to dashboardCite

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Resonant X-ray scattering study of perovskite-type vanadate RVO₃

Resonant x-ray diffraction of the magnetoresistant perovskitePr0.6Ca0.4MnO
Grenier
¹
,
Hill
²
,
Gibbs
³

et al. 2004
Phys. Rev. B
102
5
71
1
View full text Add to dashboard Cite