Electron Spin Resonance of Fe<sup>3+</sup> in SrTiO<sub>3</sub> with Special Reference to the 110°K Phase Transition

Unoki, Hiromi; Sakudo, Tunetaro

doi:10.1143/jpsj.23.546

Cited by 454 publications

(199 citation statements)

References 15 publications

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“…Undoped STO is known to enter into an antiferrodistortive phase by cooling below the transition temperature of ϳ100 K, 24 which is associated with slight rotations of the TiO 6 octahedra. 25 The STO antiferrodistortive transition temperature would match well with T C in BiMnO 3 . However, an undoped STO wafer substrate was investigated and showed no response of the wafer relative dielectric permittivity to the antiferrodistortive transition at ϳ100 K ͓Fig.…”

Section: Resultsmentioning

confidence: 78%

Large dielectric response to the paramagnetic-ferromagnetic transition(TC∼100 K)in multiferroic
Schmidt
¹
,
Eerenstein
²
,
Midgley
³

2009
Phys. Rev. B
34
1
21
0
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The dielectric properties of multiferroic BiMnO 3 50 nm epitaxial thin films grown on Nb-doped SrTiO 3 ͑001͒ substrates were analyzed by impedance spectroscopy between 55 and 155 K. One single intrinsic thin film dielectric relaxation process was deconvoluted from an extrinsic electrode interface contribution by the use of an equivalent circuit. The paramagnetic-ferromagnetic transition ͑T C ϳ 100 K͒ was reflected by a large peak in the thin film relative dielectric permittivity. The weak dielectric response at T C observed previously in BiMnO 3 polycrystals is largely enhanced in thin films. Intrinsic noninsulating thin film resistivity below T C was detected.

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Section: Resultsmentioning

confidence: 78%

Large dielectric response to the paramagnetic-ferromagnetic transition(TC∼100 K)in multiferroic
Schmidt
¹
,
Eerenstein
²
,
Midgley
³

2009
Phys. Rev. B
34
1
21
0
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“…We first calculate how freezing in the antiferrodistortive (AFD) a 0 a 0 c − octahedral tilt pattern of the lowtemperature phase of SrTiO 3 [20] affects the total energies of the two bulk materials which comprise the superlattices. Figure 1(a) shows the calculated total energies as a function of increasing amplitude of octahedral rotation angle θ, referenced to the un-rotated states at the L(S)DA equilibrium lattice parameters.…”

mentioning

confidence: 99%

Substrate coherency driven octahedral rotations in perovskite oxide films

2010

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We perform first-principles density functional calculations to explore the role of substrate proximity effects on the octahedral rotation patterns in perovskite oxide superlattices. With cubic perovskite SrFeO3 as our model film and tetragonal SrTiO3 as the substrate, we show that in most cases the substrate octahedral rotation patterns propagate into the film across the heterointerface. We also identify elastic boundary conditions for which the enforced structural coherence induces atomic displacement patterns that are not found in the bulk phase diagram of either individual constituent. We suggest that such substrate coherency-induced octahedral texturing of thin film oxides is a promising approach for tuning the electronic structure of functional oxide thin films.The use of substrate-induced bi-axial strain to modify the properties of epitaxial thin films has been demonstrated for a wide range of phenomena and materials, including mobility in semiconductors, Curie temperatures in ferromagnets and ferroelectric polarizations in complex oxides [1]. While the main effect of strain in strongly covalently bonded materials such as semiconductors is to change the bond lengths, the flexible corner-sharing networks of oxygen polyhedra in complex oxides provide additional routes for accommodating substrate-induced changes in lattice parameters. Established mechanisms include modifications of the oxygen polyhedral tilt patterns, and the formation of twin (change in orientation of long and short axes) or antiphase (variation in phase of polyhedral rotations) domains.Recently it is been suggested that, in addition to changing the lattice parameter of a complex oxide film, the presence of a heterointerface could alter the relative stability of polyhedral tilting patterns in both the film and substrate through proximity effects [2][3][4][5]. While theoretical studies have shown that strain-induced competition between polyhedral rotation modes and other lattice distortions is crucial in determining the functional properties of complex oxides [6][7][8][9][10], very little is known about the extent to which substrate proximity modifies polyhedral tilt patterns. This is in part due to difficulties in obtaining high precision measurements of oxygen positions in superlattice and thin film interfaces [11,12]. In this Letter, we use density functional theory (DFT) to calculate explicitly how the structural distortions of a substrate affect the atomic structure and properties of a coherent film.We take perovskite-structured SrFeO 3 /SrTiO 3 as our model system, chosen for its continuous A-site sublattice, absence of polar discontinuity, and simple oxygen octahedral tilt patterns: SrFeO 3 has the ideal cubic P m3m perovskite structure down to the lowest temperature studied (4 K) [13], and the ground state I4/mcm phase of SrTiO 3 (which is a widely used substrate) has a single octahedral instability with respect to the cubic phase [14] that condenses below ∼105 K. First, we investigate the effect of heterostructure periodicity in symm...

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“…Bulk STO crystals are cubic at room temperature, with space group Pm3m(O 1 h ), but become tetragonal, space group I4/mcm(D 18 4h ), below about 105K. This phase transition involves the rotation of TiO 6 octahedra and has been featured historically in the study of structural phase transitions as the classic example of a soft-mode phase transition [2]. The unit cell of the tetragonal phase has a volume four times that of the cubic unit cell, with approximate unit cell of √ 2a× √ 2a×2a, where a is the lattice parameter of cubic unit cell.…”

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confidence: 99%

Anomalous phase transition in strained SrTiO3 thin films

Wells

Shapiro

et al. 2003

Applied Physics Letters

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We have studied the cubic to tetragonal phase transition in epitaxial SrTiO3 films under various biaxial strain conditions using synchrotron X-ray diffraction. Measuring the superlattice peak associated with TiO6 octahedra rotation in the low temperature tetragonal phase indicates the presence of a phase transition whose critical temperature is a strong function of strain, with TC as much as 50K above the corresponding bulk temperature. Surprisingly, the lattice constants evolve smoothly through the transition with no indication of a phase change. This signals an important change in the nature of the phase transition due to the epitaxy strain and substrate clamping effect. The internal degrees of freedom (TiO6 rotations) have become uncoupled from the overall lattice shape.Perovskite films have received a great deal of interest lately due to the potential for creating working technologies based on a variety of interesting properties such as high-T C superconductivity, colossal magneto-resistivity, ferro-electricity, and variable dielectric constants. These properties can be quite different in thin films versus nominally similar bulk samples. The primary reasons for the changes in properties are believed to be strain and defects. There is also an emerging theoretical effort to treat the effects of strain. To understand the mechanisms for these changes we must be able to conduct detailed microscopic measurements of the atomic and electronic structure.SrTiO 3 (STO) is a nearly ferroelectric material with a large dielectric nonlinearity and low dielectric loss at cryogenic temperature, making it ideal for tunable microwave devices [1]. STO is also a good model system for studying structural phase transitions. Bulk STO crystals are cubic at room temperature, with space group Pm3m(O 1 h ), but become tetragonal, space group I4/mcm(D 18 4h ), below about 105K. This phase transition involves the rotation of TiO 6 octahedra and has been featured historically in the study of structural phase transitions as the classic example of a soft-mode phase transition [2]. The unit cell of the tetragonal phase has a volume four times that of the cubic unit cell, with approximate unit cell of √ 2a× √ 2a×2a, where a is the lattice parameter of cubic unit cell. In this paper we describe the tetragonal phase as pseudo-cubic, in order to compare the structure before and after the phase transition. In this pseudo-cubic frame, the tetragonal phase has additional superlattice peaks at half integer index positions. These superlattice peaks disappear as the temperature is raised through the tetragonal-cubic phase transition. * Present Address: HASYLAB at DESY, Notkestr. 85, 22603 Hamburg, GermanyIn the bulk, the deviation from cubic symmetry is directly related to the rotation angle of the TiO 6 octahedra. This rotation angle has been identified as the order parameter for this phase transition [3]. Correspondingly, the intensities of the superlattice peaks are proportional to the square of the order parameter and can be used to track the phas...

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Electron Spin Resonance of Fe³⁺ in SrTiO₃ with Special Reference to the 110°K Phase Transition

Cited by 454 publications

References 15 publications

Large dielectric response to the paramagnetic-ferromagnetic transition(TC∼100 K)in multiferroic
Schmidt
¹
,
Eerenstein
²
,
Midgley
³

2009
Phys. Rev. B
34
1
21
0
View full text Add to dashboard Cite

Large dielectric response to the paramagnetic-ferromagnetic transition(TC∼100 K)in multiferroic
Schmidt
¹
,
Eerenstein
²
,
Midgley
³

2009
Phys. Rev. B
34
1
21
0
View full text Add to dashboard Cite

Substrate coherency driven octahedral rotations in perovskite oxide films

Anomalous phase transition in strained SrTiO3 thin films

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Electron Spin Resonance of Fe3+ in SrTiO3 with Special Reference to the 110°K Phase Transition

Cited by 454 publications

References 15 publications

Large dielectric response to the paramagnetic-ferromagnetic transition(TC∼100 K)in multiferroicSchmidt1, Eerenstein2, Midgley3 2009Phys. Rev. B341210View full textAdd to dashboardCite

Large dielectric response to the paramagnetic-ferromagnetic transition(TC∼100 K)in multiferroicSchmidt1, Eerenstein2, Midgley3 2009Phys. Rev. B341210View full textAdd to dashboardCite

Substrate coherency driven octahedral rotations in perovskite oxide films

Anomalous phase transition in strained SrTiO3 thin films

Contact Info

Product

Resources

About

Electron Spin Resonance of Fe³⁺ in SrTiO₃ with Special Reference to the 110°K Phase Transition

Large dielectric response to the paramagnetic-ferromagnetic transition(TC∼100 K)in multiferroic
Schmidt
¹
,
Eerenstein
²
,
Midgley
³

2009
Phys. Rev. B
34
1
21
0
View full text Add to dashboard Cite

Large dielectric response to the paramagnetic-ferromagnetic transition(TC∼100 K)in multiferroic
Schmidt
¹
,
Eerenstein
²
,
Midgley
³

2009
Phys. Rev. B
34
1
21
0
View full text Add to dashboard Cite