Coupling of order parameters, chirality, and interfacial structures in multiferroic materials

Conti, Sergio; Müller, Stefan; Poliakovsky, Arkady; Salje, Ekhard K. H.

doi:10.1088/0953-8984/23/14/142203

Cited by 59 publications

(47 citation statements)

References 55 publications

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“…The observed onset of polarity related to twin walls was predicted by Morozovska et al [30] based on the coupling between the gradient of the ferroelastic order parameter and the polar displacement. The same effect was also predicted by biquadratic coupling between two order parameters, namely the tilt and the polarization [31,32]. The difference between the two coupling schemes is related to an artifact of the continuum approximation: only a few atomic layers inside the twin walls will be affected by the coupling.…”

supporting

confidence: 56%

Domains within Domains and Walls within Walls: Evidence for Polar Domains in CryogenicSrTiO3

et al. 2013

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Resonant piezoelectric spectroscopy shows polar resonances in paraelectric SrTiO 3 at temperatures below 80 K. These resonances become strong at T < 40 K. The resonances are induced by weak electric fields and lead to standing mechanical waves in the sample. This piezoelectric response does not exist in paraelastic SrTiO 3 nor at temperatures just below the ferroelastic phase transition. The interpretation of the resonances is related to ferroelastic twin walls which become polar at low temperatures in close analogy with the known behavior of CaTiO 3 . SrTiO 3 is different from CaTiO 3 , however, because the wall polarity is thermally induced; i.e., there exists a small temperature range well below the ferroelastic transition point at 105 K where polarity appears on cooling. As the walls are atomistically thin, this transition has the hallmarks of a two-dimensional phase transition restrained to the twin boundaries rather than a classic bulk phase transition.

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confidence: 56%

Domains within Domains and Walls within Walls: Evidence for Polar Domains in CryogenicSrTiO3

et al. 2013

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“…With the onset of ferroelectricity at T c near 1483 K, the structure remains trigonal, but the inversion symmetry of the system is lifted, reducing symmetry to the R3c space group. LiNbO 3 is hence ferroelectric but not ferroelastic below 1483 K. Domain structures consist exclusively of 180 o ferroelectric walls which are-in good approximation-strain-free in thermodynamic equilibrium while local strains may originate from coupling between the polariz ation and secondary displacements [24,25]. Non-equilibrium states in uniaxial ferroelectrics LiNbO 3 and LiTaO 3 are commonly observed as transient features when the polarity of the samples is inverted by an applied electric field [26][27][28][29].…”

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confidence: 99%

Influence of defects and domain walls on dielectric and mechanical resonances in LiNbO₃

Nataf

Aktas

Granzow

et al. 2015

J. Phys.: Condens. Matter

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Monodomain and periodically poled LiNbO 3 crystals (congruent composition) show dielectric and piezoelectric resonances between 100 K and 900 K. Dielectric measurements show resonances in some samples between 10-100 kHz. These resonances vanish under thermal anneal in monodomain crystals while they remain stable in periodically poled samples with high domain wall densities. The low activation energy of 0.18 eV suggests their electronic (bi-polaronic) origin. Resonant piezoelectric spectroscopy, RPS, shows two features in virgin samples: a relaxation peak at 420 K and a rapid hardening when the sample was slowly heated to ~500 K. The dynamic relaxation and the hardening are related to excitations and reorientations of Li defects. The relaxations and hardening are irreversibly suppressed by high temperature anneal. We do not observe domain wall related RPS resonances in annealed samples, which excludes the existence of highly charged walls. We suggest that domain walls stabilize polaronic states with (bi-)polarons located inside or near to the ferroelectric domain walls.

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“…In fact, we still lack a detailed structural and dynamical picture of the DWs, and in many cases we can only speculate about the structure-property relationships at work within them. Hence, there is a pressing need for predictive theoretical studies tackling the DWs at an atomistic level and at the relevant conditions of temperature, etc.The DW structure, and even the possible occurrence of DW-confined ferroic orders, have been discussed theoretically for decades, usually in the framework of continuum Ginzburg-Landau or phenomenological model theories [12][13][14][15][16][17][18][19][20][21][22]. Materials with competing structural instabilities have been a focus of attention, a good example being perovskite SrTiO 3 (STO).…”

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Ferroelectric Transitions at Ferroelectric Domain Walls Found from First Principles

2014

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We present a first-principles study of model domain walls (DWs) in prototypic ferroelectric PbTiO3. At high temperature the DW structure is somewhat trivial, with atoms occupying highsymmetry positions. However, upon cooling the DW undergoes a symmetry-breaking transition characterized by a giant dielectric anomaly and the onset of a large and switchable polarization. Our results thus corroborate previous arguments for the occurrence of ferroic orders at structural DWs, providing a detailed atomistic picture of a temperature-driven DW-confined transformation. Beyond its relevance to the field of ferroelectrics, our results highlight the interest of these DWs in the broader areas of low-dimensional physics and phase transitions in strongly-fluctuating systems.PACS numbers: 77.80. 63.70.+h, 71.15.Mb The structural domain walls (DWs) occurring in ferroelectric (FE) and ferroelastic (FS) materials have become a focus of attention. Recent studies show that the DWs can present a variety of properties, from conductive [1][2][3][4] and optical [5,6] to magnetic [7][8][9], that differ from those of the neighboring domains, which suggests that they could be the active element in nano-technological applications [10,11]. Elucidating the DW behavior poses major experimental challenges, and the origin of most of the newly discovered effects remains unclear. In fact, we still lack a detailed structural and dynamical picture of the DWs, and in many cases we can only speculate about the structure-property relationships at work within them. Hence, there is a pressing need for predictive theoretical studies tackling the DWs at an atomistic level and at the relevant conditions of temperature, etc.The DW structure, and even the possible occurrence of DW-confined ferroic orders, have been discussed theoretically for decades, usually in the framework of continuum Ginzburg-Landau or phenomenological model theories [12][13][14][15][16][17][18][19][20][21][22]. Materials with competing structural instabilities have been a focus of attention, a good example being perovskite SrTiO 3 (STO). STO undergoes a FS transition driven by an anti-ferrodistortive (AFD) mode that involves concerted rotations of the O 6 octahedra in the perovskite structure. This mode competes with a FE instability that is suppressed by the onset of the AFD distortion [23]. Yet, there are both theoretical and experimental indications that a polar order occurs at low temperatures within STO's FS DWs [16,[24][25][26], i.e., in the region where the otherwise dominant AFD distortions vanish. In this context, it is worth noting recent first-principles studies predicting that PbTiO 3 (PTO)[27] and related compounds [28] present a FE-AFD competition that is even stronger than the one occurring in STO. These are the ideal conditions to obtain interesting effects at structural DWs, and motivated this work.Low-temperature study.-We employed the tools of Ref. 27, which permit large-scale simulations with firstprinciples predictive power, to investigate an ideal version of the...

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Coupling of order parameters, chirality, and interfacial structures in multiferroic materials

Cited by 59 publications

References 55 publications

Domains within Domains and Walls within Walls: Evidence for Polar Domains in CryogenicSrTiO3

Domains within Domains and Walls within Walls: Evidence for Polar Domains in CryogenicSrTiO3

Influence of defects and domain walls on dielectric and mechanical resonances in LiNbO₃

Ferroelectric Transitions at Ferroelectric Domain Walls Found from First Principles

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Coupling of order parameters, chirality, and interfacial structures in multiferroic materials

Cited by 59 publications

References 55 publications

Domains within Domains and Walls within Walls: Evidence for Polar Domains in CryogenicSrTiO3

Domains within Domains and Walls within Walls: Evidence for Polar Domains in CryogenicSrTiO3

Influence of defects and domain walls on dielectric and mechanical resonances in LiNbO3

Ferroelectric Transitions at Ferroelectric Domain Walls Found from First Principles

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Influence of defects and domain walls on dielectric and mechanical resonances in LiNbO₃