Response of Acoustic Phonons to Charge and Orbital Order in the 50% Doped Bilayer Manganite<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>LaSr</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Mn</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>7</mml:mn></mml:msub></mml:math>

Weber, F.; Rosenkranz, Stephan; Castellan, J. P.; Osborn, R.; Zheng, Hong; Mitchell, J. F.; Chen, Y.; Chi, Songxue; Lynn, J. W.; Reznik, D.

doi:10.1103/physrevlett.107.207202

Cited by 11 publications

(9 citation statements)

References 38 publications

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“…It is interesting to compare the results in MgV 2 O 4 to metallic systems with acoustic instabilities. Our results show similarities to the measurements by F. Weber et al 71 who determined the dispersion of the TA-phonons in a metallic manganite. In this material, a charge and orbital ordering (COO) sets in at low temperatures.…”

Section: Discussionsupporting

confidence: 91%

“…In this material, a charge and orbital ordering (COO) sets in at low temperatures. Above T COO , F. Weber et al 71 report a softening of the TA phonon at q = 1 4 1 4 0 by ∆E ≈ 0.25 meV accompanied by an increase in linewidth ∆Γ HW HM ≈ 0.25 meV. Similar anomalies have been reported in other metallic manganites on decreasing temperature.…”

Section: Discussionsupporting

confidence: 65%

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Transverse acoustic phonon anomalies at intermediate wave vectors in MgV2O4

et al. 2017

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Magnetic spinels (with chemical formula AX2O4, with X a 3d transition metal ion) that also have an orbital degeneracy are Jahn-Teller active and hence possess a coupling between spin and lattice degrees of freedom. At high temperatures, MgV2O4 is a cubic spinel based on V 3+ ions with a spin S=1 and a triply degenerate orbital ground state. A structural transition occurs at TOO=63 K to an orbitally ordered phase with a tetragonal unit cell followed by an antiferromagnetic transition of TN =42 K on cooling. We apply neutron spectroscopy in single crystals of MgV2O4 to show an anomaly for intermediate wavevectors at TOO associated with the acoustic phonon sensitive to the shear elastic modulus (C11 − C12) /2. On warming, the shear mode softens for momentum transfers near close to half the Brillouin zone boundary, but recovers near the zone centre. High resolution spin-echo measurements further illustrate a temporal broadening with increased temperature over this intermediate range of wavevectors, indicative of a reduction in phonon lifetime. A subtle shift in phonon frequencies over the same range of momentum transfers is observed with magnetic fields. We discuss this acoustic anomaly in context of coupling to orbital and charge fluctuations. This is a pre-print of our paper at https://link.aps.org

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Section: Discussionsupporting

confidence: 91%

Section: Discussionsupporting

confidence: 65%

Transverse acoustic phonon anomalies at intermediate wave vectors in MgV2O4

et al. 2017

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“…2(b) is given by v s d −1 where d is obtained from the nominal layer thicknesses (estimated from x-ray reflectivity measurements) and v s = 7 17 v s,YBCO + 10 17 v manganite is the weighted average of the c-axis speed of sound in the two materials (here we are using the most common 7 nm YBCO layer and 10 nm manganite layer thicknesses) 21 . The value of v s is 4750 ± 200 m.s −1 as determined from the bulk-moduli and densities 34,35 , but similar values are obtained from other measurements of the speed of sound [36][37][38][39] .The width of the line in Fig. 2(b) comes from the uncertainty in v s for the individual YBCO and manganite layers.…”

supporting

confidence: 79%

Backfolded acoustic phonons in metal-oxide superlattices

Lyzwa,

Chan,

Khmaladze

et al. 2019

Preprint

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We report the observation of low-frequency modes in the Raman spectra of thin-film superlattices of the hightemperature superconductor YBa 2 Cu 3 O 7−δ and various manganite perovskites. Our study shows that these modes are caused by the backfolding of acoustic phonons due to the additional periodicity introduced by the superlattice. Such modes were previously only observed for ultra-pure semiconductor superlattices. They can be used to determine the bilayer thickness of the superlattice and its speed of sound. Moreover, we use the spatial resolution of Raman microscopy to map the film thickness inhomogeneity across a sample, making these modes a useful tool to characterize thin-film superlattices.

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“…2(b) is given by v s d −1 , where d is obtained from the nominal layer thicknesses (estimated from x-ray reflectivity measurements) and v s = 7 17 v s,YBCO + 10 17 v s,manganite is the weighted average of the caxis speed of sound in the two materials (here we are using the most common 7-nm YBCO layer and 10-nm manganite layer thicknesses) [24]. The value of v s is 4750 ± 200 m s −1 as determined from the bulk moduli and densities [39,40], but similar values are obtained from other measurements of the speed of sound [41][42][43][44]. The width of the line in Fig.…”

Section: B Sample Dependencementioning

confidence: 65%

Backfolded acoustic phonons as ultrasonic probes in metal-oxide superlattices

Lyzwa

Chan

Khmaladze

et al. 2020

Phys. Rev. Materials

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Ultrasonics have been an incisive probe of internal interfaces in a wide variety of systems ranging from stars to solids. For thin-film structures, however, ultrasound is largely ineffective because the signal is dominated by the substrate. Using confocal Raman spectromicroscopy, we show that multiple reflection of sound waves at internal interfaces of a metal-oxide superlattice generates standing waves that are insensitive to the substrate. Such modes had previously been observed only in high-quality superlattices of elemental semiconductors, and their observation in complex metal-oxide heterostructures is testimony to recent progress in this field. We use the high spatial resolution of the Raman microscope to demonstrate the high sensitivity of the mode frequency to atomic-scale thickness variations of the superlattice. Spectroscopy of acoustic standing waves can hence serve as a powerful characterization tool of thin-film structures. In analogy to ultrasound spectroscopy of bulk solids, lineshape analysis of these modes has the potential to yield detailed information about the internal structure of the interfaces as well as the coupling of sound waves to the low-frequency spin, charge, and orbital dynamics in metal-oxide superlattices.

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Response of Acoustic Phonons to Charge and Orbital Order in the 50% Doped Bilayer ManganiteLaSr2Mn2O7

Cited by 11 publications

References 38 publications

Transverse acoustic phonon anomalies at intermediate wave vectors in MgV2O4

Transverse acoustic phonon anomalies at intermediate wave vectors in MgV2O4

Backfolded acoustic phonons in metal-oxide superlattices

Backfolded acoustic phonons as ultrasonic probes in metal-oxide superlattices

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