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Materials
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Polar and Magnetic Relaxors and Other Cluster Glasses
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Polar and Magnetic Relaxors and Other Cluster Glasses

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Thin Films and Interfaces".

Deadline for manuscript submissions: closed (20 May 2022) | Viewed by 4117

Special Issue Editor

Prof. Dr. Jan Dec

E-Mail Website
Guest Editor
Institute of Materials Sciences, University of Silesia, Katowice, Poland
Interests: relaxor ferroelectrics; domain structure of ferroelectrics; low-frequency dielectric relaxation; non-linear dielectric response; mesoscopic disorder in ferroics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Ferromagnetics and ferroelectrics (generally referred to as ferroics) represent a family of materials with collective features reaching spontaneous, stable long-range ordered states of matter. In addition to that, these (orientation) states may be reversed under the action of an external field. Very often such a switching process manifests a respective hysteresis loop.

On the other hand, short-range ordered states of matter have recently attracted a great deal of attention. These kinds of materials comprise mesoscopic ferroic glasses such as relaxor ferroelectrics or magnetic cluster glasses. In such systems quenched statistical fluctuations of short-ranged interactions generate the ferroic clusters, while long-ranged dipolar electric/magnetic or quadrupolar stress field interactions may stabilize their glassy disorder on mesoscopic length scales. Another possible scenario may originate from geometrical frustration, where the interacting elementary units tend to stick to anomalous positions. Furthermore, chemical heterogeneity of cationic site occupation may also be considered a possible reason for intrinsic disorder. As a consequence, one obtains very complex systems that demand intense research activity. These materials may also offer unique potential for the development of new electronic devices.

The forthcoming Special Issue on “Polar and Magnetic Relaxors and Other Cluster Glasses” will cover a broad range of their physical properties, technological aspects, and potential applications with new advances in this attractive field of research. It is our pleasure to invite you to contribute your research paper, communication, or review for this Special Issue.

Prof. Jan Dec
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • ferroelectrics
  • ferromagnetics
  • ferroics
  • relaxors
  • dipolar glasses
  • spin glasses
  • mesoscopic glasses
  • frustrated materials
  • domains
  • nano-domains
  • polar nanoregions
  • clusters

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Published Papers (2 papers)

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Research

9 pages, 19759 KiB  
Article
Polar Phonon Behaviour in Polycrystalline Bi-Doped Strontium Titanate Thin Films
by Alexander Tkach, Olena Okhay, Dmitry Nuzhnyy, Jan Petzelt and Paula M. Vilarinho
Materials 2021, 14(21), 6414; https://doi.org/10.3390/ma14216414 - 26 Oct 2021
Cited by 3 | Viewed by 1587
Abstract
Strontium titanate-based materials with ferroelectric or relaxor-like properties have drawn vast attention as polar dielectrics for electronics and telecommunications. Here, we study the lattice dynamics in sol–gel-derived Sr1−1.5xBixTiO3 thin films with x = 0.0053 and 0.167, deposited on [...] Read more.
Strontium titanate-based materials with ferroelectric or relaxor-like properties have drawn vast attention as polar dielectrics for electronics and telecommunications. Here, we study the lattice dynamics in sol–gel-derived Sr1−1.5xBixTiO3 thin films with x = 0.0053 and 0.167, deposited on Al2O3 substrates, using a variable-temperature far-infrared spectroscopy in a transmittance mode. Bi doping, known to induce a low-frequency dielectric relaxation in SrTiO3 (ST) ceramics and films, due to off-centre dopant ion displacements generating electric dipoles, is shown to affect the polar phonon behaviour of thin films. We show that in weakly Bi-doped films, the low-frequency polar TO1 mode softens on cooling but less than in undoped ST. In heavily Bi-doped ST films, this mode displays no significant frequency variation with temperature from 300 to 10 K. The polar phonon behaviour of polycrystalline Bi-doped ST thin films is comparable with that of Bi-doped ST ceramics, which exhibit dielectric relaxations and harden soft-mode behaviour instead of the ferroelectric phase transition. Full article
(This article belongs to the Special Issue Polar and Magnetic Relaxors and Other Cluster Glasses)
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11 pages, 1516 KiB  
Article
Dielectric Relaxation, Local Structure and Lattice Dynamics in Mn-Doped Potassium Tantalate Ceramics
by Alexander Tkach, Abilio Almeida, Igor Levin, Joseph C. Woicik and Paula M. Vilarinho
Materials 2021, 14(16), 4632; https://doi.org/10.3390/ma14164632 - 17 Aug 2021
Cited by 2 | Viewed by 1860
Abstract
Alkaline niobate and tantalate perovskites have attracted attention as polar dielectrics for electronics and telecommunications. Here, we studied the polar behaviour, lattice dynamics, and local structure in conventionally processed K0.985Mn0.015TaO3±δ ceramics using a combination of variable-temperature dielectric and [...] Read more.
Alkaline niobate and tantalate perovskites have attracted attention as polar dielectrics for electronics and telecommunications. Here, we studied the polar behaviour, lattice dynamics, and local structure in conventionally processed K0.985Mn0.015TaO3±δ ceramics using a combination of variable-temperature dielectric and Raman spectroscopies, and X-ray absorption fine structure (XAFS) measurements, respectively. Mn doping induces a low-frequency dielectric relaxation in KTaO3 (KT), which follows the Arrhenius law with an activation energy U ≈ 105 meV and the characteristic relaxation time τ0 ≈ 4.6 × 10−14 s. Our XAFS results support preferential Mn occupancy of the cuboctahedral sites as Mn2+, with these cations strongly off-centred in the oversized oxygen cages. Such disordered Mn displacements generate electric dipoles, which are proposed as the source of the observed dielectric relaxation. We show that in Mn-doped ceramics, the low-frequency polar TO1 mode softens on cooling and, at low temperatures, exhibits a higher frequency than in undoped KT. This mode displays no detectable splitting, which contrasts with Li-doped KT that also contains off-centred Li+ species on the cuboctahedral sites. Therefore, we conclude that the coupling between the Mn displacements and the lattice is weaker than in the Li case, and Mn-doped KT therefore exhibits a dielectric relaxation but no ferroelectric transition. Full article
(This article belongs to the Special Issue Polar and Magnetic Relaxors and Other Cluster Glasses)
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