Elastic relaxations associated with the Pm\bar {3}m –R\bar {3}c transition in LaAlO<sub>3</sub>: III. Superattenuation of acoustic resonances

Carpenter, Michael A.; Buckley, A.; Taylor, Paul A.; Darling, T. W.

doi:10.1088/0953-8984/22/3/035405

Cited by 58 publications

(111 citation statements)

References 75 publications

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“…Superimposed on the classical picture is softening as T → T c from above due to fluctuations. This is again typical of octahedral tilting transitions in perovskites, such as SrTiO 3 [36], SrZrO 3 [41], LaAlO 3 [42], and KMnF 3 [43], for example. The elastic constants do not by themselves give a precise transition temperature, but there are no gross features in the resonance frequencies that would indicate phase transitions at any temperature other than that indicated by the heat capacity anomaly as occurring at T c = 284 K.…”

Section: Discussionmentioning

confidence: 76%

“…The freezing interval where the walls become pinned by the defects is then marked by a Debye loss peak near 450 K. Under the higher frequency (∼1 MHz) and relatively low stress conditions of a RUS experiment, acoustic losses are sufficiently high that details of the plateau region are not seen because resonance peaks are totally attenuated (superattenuation). The pinning process is still complete by ∼400 K, however [42]. If the twin walls in EuTiO 3 are subject to pinning by oxygen vacancies, as in LaAlO 3 , it is likely that their freezing interval will also be in the vicinity of ∼450 K, i.e., well above T c .…”

Section: Discussionmentioning

confidence: 99%

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Elastic and anelastic relaxations associated with phase transitions inEuTiO3

et al. 2014

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Elastic and anelastic properties of single crystal samples of EuTiO 3 have been measured between 10 and 300 K by resonant ultrasound spectroscopy at frequencies in the vicinity of 1 MHz. Softening of the shear elastic constants C 44 and 1 2 (C 11 − C 12 ) by ∼20-30% occurs with falling temperature in a narrow interval through the transition point, T c = 284 K, for the cubic-tetragonal transition. This is accounted for by classical coupling of macroscopic spontaneous strains with the tilt order parameter in the same manner as occurs in SrTiO 3 . A peak in the acoustic loss occurs a few degrees below T c and is interpreted in terms of initially mobile ferroelastic twin walls, which rapidly become pinned with further lowering of temperature. This contrasts with the properties of twin walls in SrTiO 3 , which remain mobile down to at least 15 K. No further anomalies were observed that might be indicative of strain coupling to any additional phase transitions above 10 K. A slight anomaly in the shear elastic constants, independent of frequency and without any associated acoustic loss, was found at ∼140 K. It marks a change from elastic stiffening to softening with falling temperature and perhaps provides evidence for coupling between strain and local fluctuations of dipoles related to the incipient ferroelectric transition. An increase in acoustic loss below ∼80 K is attributed to the development of dynamical magnetic clustering ahead of the known antiferromagnetic ordering transition at ∼5.5 K. Detection of these elastic anomalies serves to emphasize that coupling of strain with tilting, ferroelectric, and magnetic order parameters is likely to be a permeating influence in determining the structure, stability, properties, and behavior of EuTiO 3 .

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Section: Discussionmentioning

confidence: 76%

Section: Discussionmentioning

confidence: 99%

Elastic and anelastic relaxations associated with phase transitions inEuTiO3

et al. 2014

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“…The elastic properties of LaAlO 3 measured at RUS frequencies are dominated by intrinsic effects from strain/order parameter coupling and the anelastic losses have been understood in terms of local and rather limited displacements of the twin walls [43]. Twin walls in purely ferroelastic materials tend to have thicknesses corresponding to just a few unit cells [51], whereas magnetic domain walls are typically much thicker than this.…”

Section: Ferroelastic Properties Of Ndcomentioning

confidence: 99%

Multiferroic (ferroelastic/ferromagnetic/ferrimagnetic) aspects of phase transitions in RCo₂Laves phases

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Herrero‐Albillos

Bonilla

et al. 2014

J. Phys.: Condens. Matter

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Magnetic phase transitions in RCo 2 Laves phases with R as a rare earth element are accompanied by changes in crystallographic space group. For purely structural transitions they would be described as improper ferroelastic and therefore fulfil the condition for multiferroic phase transitions in combining two out of three properties, ferro/antiferromagnetism, ferroelectricity and ferroelasticity. Here lattice parameter data from the literature and new measurements of elastic and anelastic properties, by resonant ultrasound spectroscopy, for NdCo 2 and ErCo 2 have been analysed from this perspective. The temperature dependence of symmetry-breaking shear strains is consistent with the cubic ↔ tetragonal transition in NdCo 2 being close to tricritical in character and the cubic ↔ rhombohedral transition in ErCo 2 being first order. Elastic softening and acoustic loss within the stability ranges of the ferroelastic phases can be understood in terms of a combination of intrinsic softening due to strain/order parameter coupling and ferroelastic twin-wall motion. Softening ahead of the transitions does not fit with standard macroscopic descriptions of dynamic effects from other systems but, rather, in the case of NdCo 2 , might be attributed to the involvement of a second zone centre order parameter related to a separate instability driven by cooperative Jahn-Teller distortions. In ErCo 2 , acoustic loss in the temperature interval above the transition point is discussed in terms of a possible tweed microstructure associated with strain coupling to local magnetic ordering. The overall multiferroic behaviour can be understood in terms of a single magnetic order parameter (irrep m + 4 of magnetic space group Fd3m1 ) which couples with a structural order parameter (irrep + 3 or + 5 ). The coupling is linear/quadratic which, in the case of two separate instabilities, causes them to combine in a single multiferroic phase transition.

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“…The value of the exponent j, between 1/2 and 2, depends on the anisotropy and dispersion of soft branches round the critical point of the soft mode [133][134][135][136][137] as has been found for precursor softening in SrTiO 3 , LaAlO 3 and KMnF 3 , for example [138][139][140]. If, on the other hand, the softening is due to relaxorlike freezing processes, it would be better represented by a Vogel-Fulcher equation…”

Section: Precursor Softeningmentioning

confidence: 99%

“…Extrapolation of Arrhenius solutions for the frequency and temperature dependence would put the equivalent freezing process near 800 K when measured at *500 kHz, however, implying that the same loss mechanism will not be detected in RUS data. It has been argued elsewhere, firstly, that displacements of ferroelastic twin walls can occur by at least two mechanisms, the advance/retraction of needle tips or the sideways migration of small ledges, and, secondly, that the latter will dominate under the relatively low stress and high-frequency conditions characteristic of RUS measurements [138,146,147]. On this basis, the lowfrequency Debye peaks would be due to freezing of the needle tip motion, while the loss mechanism responsible for the superattenuation observed here is motion of ledges along the twin walls.…”

Section: Twin Wall Dynamics and Evidence For Local Strain Heterogeneitymentioning

confidence: 99%

Elastic and anelastic relaxation behaviour of perovskite multiferroics I: PbZr0.53Ti0.47O3 (PZT)–PbFe0.5Nb0.5O3 (PFN)

et al. 2016

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Perovskites in the ternary system PbTiO 3 (PT)-PbZrO 3 (PZ)-Pb(Fe 0.5 Nb 0.5 )O 3 (PFN) have attracted close interest because they can display simultaneous ferroelectric, magnetic and ferroelastic properties. Those with the most sensitive response to external fields are likely to have compositions near the morphotropic phase boundary (MPB) which lies close to the binary join Pb(Zr 0.53 Ti 0.47 )O 3 (PZT)-PFN. In the present study, the strength and dynamics of strain coupling behaviour which accompanies the development of ferroelectricity and (anti)ferromagnetism in ceramic PZT-PFN samples have been investigated by resonant ultrasound spectroscopy. Elastic softening ahead of the cubic-tetragonal transition does not fit with models based on dispersion of the soft mode or relaxor characteristics but is attributed, instead, to coupling between acoustic modes and a central peak mode from correlated relaxations and/or microstructure dynamics. Softening of the shear modulus through the transition by up to *50 % fits with the expected pattern for linear/quadratic strain/order parameter coupling at an improper ferroelastic transition and close to tricritical evolution for the order parameter. Superattenuation of acoustic resonances in a temperature interval of *100 K below the transition point is indicative of mobile ferroelastic twin walls. By way of contrast, the first-order tetragonalmonoclinic transition involves only a small change in the shear modulus and is not accompanied by significant changes in acoustic dissipation. The dominant Address correspondence to E-mail: mc43@esc.cam.ac.uk DOI 10.1007/s10853-016-0280-2 J Mater Sci (2016) 51:10727-10760 feature of the elastic and anelastic properties at low temperatures is a concaveup variation of the shear modulus and relatively high loss down to the lowest temperature, which appears to be the signature of materials with substantial local strain heterogeneity and a spectrum of strain relaxation times. No evidence of magnetoelastic coupling has been found, in spite of the samples displaying ferromagnetism below *550 K and possible spin glass ordering below *50 K. For the important multiferroic perovskite ceramics with compositions close to the MPB of ternary PT-PZ-PFN, there must be some focus in future on the role of strain heterogeneity.

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Elastic relaxations associated with the Pm\bar {3}m –R\bar {3}c transition in LaAlO₃: III. Superattenuation of acoustic resonances

Cited by 58 publications

References 75 publications

Elastic and anelastic relaxations associated with phase transitions inEuTiO3

Elastic and anelastic relaxations associated with phase transitions inEuTiO3

Multiferroic (ferroelastic/ferromagnetic/ferrimagnetic) aspects of phase transitions in RCo₂Laves phases

Elastic and anelastic relaxation behaviour of perovskite multiferroics I: PbZr0.53Ti0.47O3 (PZT)–PbFe0.5Nb0.5O3 (PFN)

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Elastic relaxations associated with the Pm\bar {3}m –R\bar {3}c transition in LaAlO3: III. Superattenuation of acoustic resonances

Cited by 58 publications

References 75 publications

Elastic and anelastic relaxations associated with phase transitions inEuTiO3

Elastic and anelastic relaxations associated with phase transitions inEuTiO3

Multiferroic (ferroelastic/ferromagnetic/ferrimagnetic) aspects of phase transitions in RCo2Laves phases

Elastic and anelastic relaxation behaviour of perovskite multiferroics I: PbZr0.53Ti0.47O3 (PZT)–PbFe0.5Nb0.5O3 (PFN)

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Elastic relaxations associated with the Pm\bar {3}m –R\bar {3}c transition in LaAlO₃: III. Superattenuation of acoustic resonances

Multiferroic (ferroelastic/ferromagnetic/ferrimagnetic) aspects of phase transitions in RCo₂Laves phases