Phase diagram of LaTiO x : from 2D layered ferroelectric insulator to 3D weak ferromagnetic semiconductor

Lichtenberg, F.; Widmer, Daniel; Bednorz, J. G.; Williams, Tim; Reller, Armin

doi:10.1007/bf01324328

Cited by 101 publications

(70 citation statements)

References 12 publications

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“…The decrease in resistance (or equivalently, the increase in conductivity) with increasing dimensionality is consistent with other work on similar materials [12][13][14][15]. Samples with n = 6 were found to form more readily within the Nd n Ti n O 3n+2 system, compared to the corresponding La n Ti n O 3n+2 system.…”

Section: Discussionsupporting

confidence: 87%

“…Studies of the electrical properties of systems where there is a crossover from 2-dimensional to 3-dimensional structures generally show that the conductivity increases with the dimensionality [12,13]. Conductivity measurements on the closely related La n Ti n O 3n+2 system show a large increase in conductivity of La 5 Ti 5 O 17 compared to La 4 Ti 4 O 14 [14,15].…”

Section: Introductionmentioning

confidence: 99%

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Electrical properties of the arc-melted, layered-perovskite system NdnTinO3n+2 with n=4.5–6.5

Connolly¹,

Tilley²

2012

Journal of Alloys and Compounds

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Section: Discussionsupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Electrical properties of the arc-melted, layered-perovskite system NdnTinO3n+2 with n=4.5–6.5

Connolly¹,

Tilley²

2012

Journal of Alloys and Compounds

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“…Details concerning the crystal growth and characterization have been described in [86] for TiOCl, in [35,87] for RTiO 3 , in [88] for LaMnO 3 , in [89,90] Using a Fourier-transform spectrometer, we have measured the transmittance and reflectance in the energy range from 0.01 eV up to 3 eV at temperatures varying from 4 to 775 K. With the knowledge of both transmittance and reflectance, it is possible to directly calculate the complex optical conductivity σ(ω) [93]. For the transmittance measurements, the samples were polished on both sides.…”

Section: Methodsmentioning

confidence: 99%

Optical study of orbital excitations in transition-metal oxides

et al. 2005

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Collective orbital excitations in orbitally ordered YVO3 and HoVO3 E Benckiser, R Rückamp, T Möller et al. Abstract. The orbital excitations of a series of transition-metal compounds are studied by means of optical spectroscopy. Our aim was to identify signatures of collective orbital excitations by comparison with experimental and theoretical results for predominantly local crystal-field excitations. To this end, we have studied TiOCl, RTiO 3 (R = La, Sm and Y), LaMnO 3 , Y 2 BaNiO 5 , CaCu 2 O 3 and K 4 Cu 4 OCl 10 , ranging from early to late transition-metal ions, from t 2g to e g systems, and including systems in which the exchange coupling is predominantly three-dimensional, one-dimensional or zero-dimensional. With the exception of LaMnO 3 , we find orbital excitations in all compounds. We discuss the competition between orbital fluctuations (for dominant exchange coupling) and crystal-field splitting (for dominant coupling to the lattice). Comparison of our experimental results with configuration-interaction cluster calculations in general yields good agreement, demonstrating that the coupling to the lattice is important for a 7 Author to whom any correspondence should be addressed. quantitative description of the orbital excitations in these compounds. However, detailed theoretical predictions for the contribution of collective orbital modes to the optical conductivity (e.g. the line shape or the polarization dependence) are required to decide on a possible contribution of orbital fluctuations at low energies, in particular, in case of the orbital excitations at ≈0.25 eV in RTiO 3 . Further calculations are called for which take into account the exchange interactions between the orbitals and the coupling to the lattice on an equal footing. Contents

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“…LaTiO 3 has the tendency to incorporate La and Ti vacancies which are frequently denoted by an excess of oxygen in the formula LaTiO 3+δ . By adjusting the ratio of TiO and TiO 2 in the starting materials [9] one may vary the final oxygen content of the samples. Stoichiometry was verified by thermogravimetric analyzes and by determining the Néel-temperature in a SQUID magnetometer.…”

mentioning

confidence: 99%

Crystal and magnetic structure ofLaTiO3:Evidence for nondegeneratet2g
Cwik
¹
,
Lorenz
²
,
Baier
³

et al. 2003
Phys. Rev. B
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The crystal and magnetic structure of LaTiO3 has been studied by x-ray and neutron diffraction techniques using nearly stoichiometric samples. We find a strong structural anomaly near the antiferromagnetic ordering, TN =146 K. In addition, the octahedra in LaTiO3 exhibit an intrinsic distortion which implies a splitting of the t2g-levels. Our results indicate that LaTiO3 should be considered as a Jahn-Teller system where the structural distortion and the resulting level splitting are enhanced by the magnetic ordering.LaTiO 3 has been studied already in the seventies and was thought to be a text book example of a Mottinsulator with antiferromagnetic order [1]. Ti is in its three-valent state with a single electron in the t 2g -orbitals of the 3d-shell. The titanate is hence an electron analog to the cuprates with a single hole in the 3d-shell. However, the t 2g -orbitals in the LaTiO 3 are less Jahn-Teller active and, therefore, the orbital moment may not be fully quenched in the titanate. The physics of the orbital degree of freedom has recently reattracted attention to this material [2,3].The ordered moment in LaTiO 3 amounts to 0.46 µ B which is much smaller than the value of 1µ B expected for a single electron with quenched orbital moment [4]. Quantum fluctuations can explain only about 15% reduction in the 3D-case. A straight-forward explanation could be given in terms of spin-orbit coupling, as an unquenched orbital moment would align antiparallel to the spin-moment in the titanate. However, in a recent neutron scattering experiment the magnon spin gap was observed at 3.3 meV, and it was argued that the strong interaction of an orbital moment with the crystal lattice implies a much larger value for the spin gap [2]. An orbital contribution to the ordered moment in LaTiO 3 was hence excluded. On the basis of standard theories, however, even the G-type antiferromagnetic ordering in LaTiO 3 may not be explained without a spinorbit coupling. Instead one expects ferromagnetism [5,6] related with the orbital degeneracy. Under the assumption of a specific structural distortion, Moshizuki and Imada recently presented a successful model for the antiferromagnetic order in LaTiO 3 [7]. However, there is no experimental evidence for such a distortion. The puzzling magnetic properties of LaTiO 3 led Khaliullin and Maekawa to suggest a novel theoretical description for RETiO 3 based on the idea of an orbital liquid. They were able to explain many of the magnetic characteristics of LaTiO 3 [3], but the presumed orbital fluctuations have not been observed [8]. Therefore, magnetism in LaTiO 3 still remains an open issue.We have reanalyzed the crystal and magnetic structure of LaTiO 3 by x-ray and by neutron diffraction samples with almost perfect stoichiometry. First, we find a clear structural anomaly at the Néel-ordering and, second, the shape of the octahedra in this compound is not ideal but distorted. From these observations we conclude that LaTiO 3 has to be considered as a soft Jahn-Teller system thereby explaining m...

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Phase diagram of LaTiO x : from 2D layered ferroelectric insulator to 3D weak ferromagnetic semiconductor

Cited by 101 publications

References 12 publications

Electrical properties of the arc-melted, layered-perovskite system NdnTinO3n+2 with n=4.5–6.5

Electrical properties of the arc-melted, layered-perovskite system NdnTinO3n+2 with n=4.5–6.5

Optical study of orbital excitations in transition-metal oxides

Crystal and magnetic structure ofLaTiO3:Evidence for nondegeneratet2g
Cwik
¹
,
Lorenz
²
,
Baier
³

et al. 2003
Phys. Rev. B
Self Cite
207
32
222
1
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Phase diagram of LaTiO x : from 2D layered ferroelectric insulator to 3D weak ferromagnetic semiconductor

Cited by 101 publications

References 12 publications

Electrical properties of the arc-melted, layered-perovskite system NdnTinO3n+2 with n=4.5–6.5

Electrical properties of the arc-melted, layered-perovskite system NdnTinO3n+2 with n=4.5–6.5

Optical study of orbital excitations in transition-metal oxides

Crystal and magnetic structure ofLaTiO3:Evidence for nondegeneratet2gCwik1, Lorenz2, Baier3 et al. 2003Phys. Rev. BSelf Cite207322221View full textAdd to dashboardCite

Contact Info

Product

Resources

About

Crystal and magnetic structure ofLaTiO3:Evidence for nondegeneratet2g
Cwik
¹
,
Lorenz
²
,
Baier
³

et al. 2003
Phys. Rev. B
Self Cite
207
32
222
1
View full text Add to dashboard Cite