EPR of Jahn‐Teller polarons in oxide perovskites

Schirmer, O. F.; Kool, Th. W.; Lenjer, S.; Maiwald, Martin

doi:10.1002/pssc.200460127

Cited by 5 publications

(3 citation statements)

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“…The magnetic properties of JT ions with nd 1 electron configurations were investigated in detail in SrTiO 3 :Cr 5+ [11-15], SrTiO 3 :V 4+ [29,30], SrTiO 3 :Mo 5+ [31], BaTiO 3 :Ti 3+ [9,[32][33][34] and BaTiO 3 :Mo 5+ [34,35]. The prevailing tetragonal symmetry and the magnetic parameters of nd 1 ions could consistently be explained assuming a JT coupling between the 2 T 2g electronic ground state with a localized phonon mode of e symmetry in the strong coupling regime (T 2 ⊗ e JTE) [36].…”

Section: Discussionmentioning

confidence: 99%

The Jahn–Teller effect in Cr⁵⁺-doped PbTiO₃: a multi-frequency electron paramagnetic resonance study

Böttcher

Pöppl

Hoentsch

et al. 2010

J. Phys.: Condens. Matter

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Electron paramagnetic resonance (EPR) spectra of Cr5+ defects incorporated on Ti(4+) sites in powdered ceramics of PbTiO3 were investigated in the temperature range 50-400 K at 9 GHz (X), 34 GHz (Q) and 94 GHz (W band). The [Formula: see text] Jahn-Teller effect stabilizes the vibronic ground state of the 3d(1) electron of the Cr(5+) ion and leads to a tetragonally distorted defect- O6 octahedron with the point symmetry D(4h). The spontaneous electrical polarization present in the ferroelectric phase of PbTiO3 appears as a further perturbation producing an additional g-tensor contribution by the quadratic field effect. Its symmetry is dependent on the orientation of the electrical polarization with respect to the Jahn-Teller distortion axis, the tetragonal axis of the defect- O6 octahedron. If the polarization of a domain is anti- or parallel to this axis, the local tetragonal symmetry of the Cr5+ ion persists whereas it is reduced by a perpendicular orientation. Anisotropic EPR spectra of tetragonally and orthorhombic distorted Cr(5+)O6(12-) are detected at low temperatures. Increasing the temperature, the peaks of the two spectra are broadened and a motionally averaged isotropic spectrum appears at 200 K.

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Section: Discussionmentioning

confidence: 99%

The Jahn–Teller effect in Cr⁵⁺-doped PbTiO₃: a multi-frequency electron paramagnetic resonance study

Böttcher

Pöppl

Hoentsch

et al. 2010

J. Phys.: Condens. Matter

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“…The magnetic properties of JT ions with nd 1 electron configurations were investigated in detail in SrTiO 3 :Cr 5+ [2-6], SrTiO 3 :V 4+ [17] BaTiO 3 :Ti 3+ [18][19][20][21] and BaTiO 3 :Mo 5+ [21,22]. The prevailing tetragonal symmetry and the magnetic parameters of nd 1 ions could consistently be explained assuming a JT coupling between the 2 T 2g electronic ground state with a localized phonon mode of e symmetry in the strong coupling regime (T 2 ⊗ e JTE) [23].…”

Section: Discussionmentioning

confidence: 99%

Jahn–Teller effect in BaTiO₃:Cr⁵⁺: an electron paramagnetic resonance study

Böttcher

Langhammer

Müller

2009

J. Phys.: Condens. Matter

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Electron paramagnetic resonance (EPR) spectra of Cr(I)(5+) defects incorporated on Ti(4+) sites in single-crystal and powdered ceramics of BaTiO(3) were investigated in the temperature range 50-220 K at 34 GHz (Q band). Single-crystal and powder measurements allow the unambiguous determination of the full g tensor in the ferroelectric rhombohedral phase whereas in the orthorhombic phase only the determination of the principal values of the Cr(I)(5+) g tensor was successful. The [Formula: see text] Jahn-Teller effect stabilizes the vibronic ground state of the 3d(1) electron of the Cr(I)(5+) ion and leads to a tetragonally compressed defect-O(6) octahedron with the point symmetry D(4h). The spontaneous electrical polarization present in the ferroelectric phases of BaTiO(3) appears as a further perturbation. The quadratic field effect reduces the D(4h) symmetry of the Cr(I)(5+) defect centre and produces an additional g tensor breaking the tetragonal symmetry of the Zeeman term. For symmetry reasons one of the principal axes of the rhombic g tensor must be directed along one [Formula: see text] direction. The angles of the other two principal axes with respect to the [Formula: see text] axes are dependent on the absolute value of the spontaneous polarization. The difference in the temperature behaviour of the single-crystal and powder spectra can be explained by the presence of internal stress in the grains of the ceramic samples which increases the JT energy of the 3d(1) electron.

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“…However, there are only a few of such optical experiments containing reliable data concerning incipient ferroelectrics at low temperatures. Whereas hole O − polarons have already been established in KTO, 13,14 BaTiO 3 ͑BTO͒, 18 and LiNbO 3 ͑LNO͒, 19 electron polarons were not proven experimentally neither in STO nor in KTO. 9͒ was tentatively attributed to transitions involving localized small electron polarons and O − hole centers.…”

Section: Introductionmentioning

confidence: 99%

Photochromism and polaronic photocharge localization in diluted KTa1−xNbxO3

Gubaev

Kapphan

Jastrabı́k

et al. 2006

Journal of Applied Physics

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Ultraviolet ͑UV͒-light-induced optical absorption in the near infrared ͑NIR͒ region was observed in diluted KTa 1−x Nb x O 3 single crystals ͑x = 0 , 0.004, 0.007, 0.012, 0.07͒ at low temperatures. Illumination by wideband light ͑3.10-4.13 eV, 300-400 nm͒ is accompanied by the appearance of a broad NIR absorption band with the position of the maxima varying in the 0.69-0.8 eV ͑1.54-1.79, T = 1.3 K͒ region for different Nb concentrations. This UV-light-induced absorption is absent in nominally pure KTaO 3 , as well as in all Nb diluted specimens at elevated temperatures. The centers responsible for the photochromic NIR absorption bands are tied to interband optical transitions of pair Nb 4+ electronic polarons. The photochromic experimental data, supplemented by luminescence studies in the visible range, evidence the strong localization of the photocharge carriers by pair Nb 4+ polarons at low temperatures. It is suggested that namely the strong localization of the photocarriers plays a crucial role in photoinduced gigantic dielectric effects and possible phase transitions, which have been recognized recently in incipient ferroelectrics at low temperatures.

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EPR of Jahn‐Teller polarons in oxide perovskites

Cited by 5 publications

References 5 publications

The Jahn–Teller effect in Cr⁵⁺-doped PbTiO₃: a multi-frequency electron paramagnetic resonance study

The Jahn–Teller effect in Cr⁵⁺-doped PbTiO₃: a multi-frequency electron paramagnetic resonance study

Jahn–Teller effect in BaTiO₃:Cr⁵⁺: an electron paramagnetic resonance study

Photochromism and polaronic photocharge localization in diluted KTa1−xNbxO3

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EPR of Jahn‐Teller polarons in oxide perovskites

Cited by 5 publications

References 5 publications

The Jahn–Teller effect in Cr5+-doped PbTiO3: a multi-frequency electron paramagnetic resonance study

The Jahn–Teller effect in Cr5+-doped PbTiO3: a multi-frequency electron paramagnetic resonance study

Jahn–Teller effect in BaTiO3:Cr5+: an electron paramagnetic resonance study

Photochromism and polaronic photocharge localization in diluted KTa1−xNbxO3

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The Jahn–Teller effect in Cr⁵⁺-doped PbTiO₃: a multi-frequency electron paramagnetic resonance study

The Jahn–Teller effect in Cr⁵⁺-doped PbTiO₃: a multi-frequency electron paramagnetic resonance study

Jahn–Teller effect in BaTiO₃:Cr⁵⁺: an electron paramagnetic resonance study