Fundamental insights on scale-dependent phenomena in barium titanate-based ferroelectrics: critical grain size and effect of nanostructuring (FerroScale)
Project code: PN-III-P4-ID-PCE-2016-0817
Project number: 192 ⁄ 2017
Funded by the Executive Unit for Financing High Education, Research, Development and Innovation, CNCS – UEFISCDI
Magnetoelectric composites with emergent properties for wireless and sensing applications (MECOMAP)
Financed by executive unit for financing education higher, research and development and innovation, CNCS – UEFISCDI, project number 263/2014, project code: PN-II-PT-PCCA-2013-4-1119
Click here for Romanian version
The aim of the present multidisciplinary project is to design by modeling&simulation, produce by innovative synthesis methods and various sintering strategies, to investigate the physico-chemical properties at various length scales of a few types of magnetoelectric composites with emergent properties in order to integrate them at industrial scale in a few types of new applications.
Spin crossover micro and nanoparticles embedded in various environments: an experimental and theoretical study
(Micro și nanoparticule cu tranzitie de spin încorporate in diverse medii: studiu experimental si teoretic)
Financed by the Romanian National Authority for Scientific Research, CNCS – UEFISCDI, project PN-II-RU-TE-2014, no. 151 / 2015
Project Director: Conf. univ. dr. Cristian ENACHESCU
(Faculty of Physics, Alexandru Ioan Cuza University, Iași)
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The project is devoted to the study of fundamental properties of nano and micro structured spin-crossover (SC) materials embedded in various media. These compounds, having two spin states with different magnetic and optical properties, are intensely studied due to their potential use in technological applications, as data storage or sensors and actuators. As the molecules also have different volumes in the two states, the SC materials are dominated by elastic interactions which trigger multi-hysteretic behavior induced by temperature, pressure or light. In addition, some micro and nanoparticles of SC materials embedded in polymers or surfactants show a huge hysteresis of mechanical nature. Their behaviour is not only influenced by the environment, but equally, in core-shell structures, the transition of shell SC materials could influence the piezoelectric properties of core materials. Therefore, the SC nanoparticles embedded in various media are interesting for potential applications due to their intrinsic properties but also due to the mechanical influence on environment. The present research will have two main directions: one experimental and the other of modeling. The experimental study of the mentioned compounds will include magnetometric and optical measurements. The experiments will be closely accompanied by a modeling effort using Monte Carlo approaches which will cover the domain from the molecular level up to and nano and microstructures.
The aim of the project is to understand the behaviour of spin crossover micro and nano particles interacting with the environment, in order to handle and apply the properties of the bistability and switching of these materials at meso and nanoscale. The long term perspective consists in clarifying the possibilities of their application for the storage of high density information, or for their use as sensors and actuators. The systematic experimental studies will be correlated and interpreted by the simultaneous use of theoretical and numerical studies. The theoretical studies will be based on the experimental data and will be used not only to explain the observations, but also for correcting the experiments and to propose new experimental procedures.
The idea of this scientific project is centred on the study of spin crossover micro and nanoparticles dispersed in various environments, either polymeric for the beginning or piezoelectric in a second stage. This idea is based on the fact that the behaviour of micro and nanoparticles embedded in various matrices is totally different comparing to free micro and nanoparticles. Due to the change of volume during the transition, not only the spin crossover compound is influenced, but also the environment. Therefore, its eventual piezoelectric properties could be controlled by the state of spin crossover compound. The hypotheses suggested by some of our preliminary results show that the effects could depend on the volume change of the particles, on elastic interactions between the particle and the molecules composing the matrices (as van der Waals forces) and on the properties of the matrix (rigidity, density, fragility, viscosity, relaxation dynamics etc)
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| Conf. Univ. Dr. Habil. Cristian ENACHESCU | Project Manager |
| Lect. Dr. Petronel POSTOLACHE | Postdoctoral Researcher |
| Drd. Flavian ZACRETCHI | Researcher Assistant |
| Drd. Alexandru ATITOAIE | Researcher Assistant |
| Fiz. Raluca-Maria STAN | Researcher Assistant |
| Fiz. Roxana GAINA | Researcher Assistant |
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The experiments will concentrate on the following objectives and activities, oriented towards the study of the thermal, optical and pressure induced bistability:
(OE1) The study of thermal spin transition in various environments
(AE1.1) Magnetic measurements of the hysteresis cycle during thermal transition and comparison of data with those in the case of free nanoparticles (these data are available for some compounds).
(AE1.2) Optical measurements of the thermal transition; finding differences from magnetic data.
(AE1.3) Measurements of the minor cycles and FORCs (First Order Reversal Curves): finding experimental FORC distributions
(OE2) The study of light on the spin transition particles
(AE2.1) Finding the best photoexcitation conditions (temperature, material amount) for photomagnetic and optical measurements
(AE2.2) Relaxation and photoexcitation measurements and comparison of data with free particles
(AE2.3) Study of the light induced thermal hysteresis and comparing the FORC distributions with those in the thermal hysteresis
(OE3) Study of combined effects of external and environmental pressure on spin transition micro and nano particles and the study of pressure hysteresis
(AE3.1) Measuring the thermal hysteresis as a function of pressure using pressure cell in SQUID
(OE4) Study of influence of spin crossover microparticles on the piezoelectric environment
(AE4.1) Conductivity measurements as a function of the spin state using specific SQUID module
Theoretical objectives will consist in modelling experimental data for samples embedded in polymers or disposed in core-shell structures.
(OT1) Analysis using Ising-like model and mean field model
(AT1.1) Use of the mean field model for finding the activation energy, enthalpy and entropy difference between the two states
(AT1.2) Application of the Ising-like model for finding the interaction parameters (both activities will be cyclically realized a function of experiments (see GAND diagram from Methodology).
(OT2) Application of the mechanoelastic model (using parameters from OT1)
(AT2.1) The study of environmental effects on nano and microstructures
(AT2.2) The study of interaction propagation as a function of elastic constants of the environment
(AT2.3) The study of the influence of spin transition particles from the shell on the inside piezoelectric material in core-shell structures.
(OM) Besides scientific objectives, a permanent objective will be the project management (acquiring new devices and consumables, opportune stages and conferences etc.).
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Reports:
Papers (click on the title for the paper)
Enachescu, C; Hauser, A Study of switching in spin transition compounds within the mechanoelastic model with realistic parameters PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Volume: 18, Issue: 30, Pages: 20591-20599, DOI: 10.1039/c6cp02806c, AUG 14 2016
Enachescu, C; Tanasa, R; Stancu, A; Tissot, A; Laisney, J; Boillot, ML Matrix-assisted relaxation in Fe(phen)(2)(NCS)(2) spin-crossover microparticles, experimental and theoretical investigations APPLIED PHYSICS LETTERS, Volume: 109, Issue: 3, Article Number: 031908, DOI: 10.1063/1.4959262, JUL 18 2016
Bertoni, R; Lorenc, M; Cailleau, H; Tissot, A; Laisney, J; Boillot, ML; Stoleriu, L; Stancu, A; Enachescu, C; Collet, E Elastically driven cooperative response of a molecular material impacted by a laser pulse NATURE MATERIALS, Volume: 15, Pages: 606, DOI: 10.1038/NMAT4606, JUN 2016
Enachescu, C.; Stoleriu, L.; Nishino, M.; Miyashita, S.; Stancu, A.; Lorenc, M.; Bertoni, R.; Cailleau, H.; Collet E, Theoretical approach for elastically driven cooperative switching of spin-crossover compounds impacted by an ultrashort laser pulse, PHYSICAL REVIEW B 95, 224107, 2017
Stoleriu, L.; Nishino, M.; Miyashita, S.; Stancu, A.; Hauser, A.; Enachescu, C Cluster evolution in molecular three-dimensional spin-crossover systems, PHYSICAL REVIEW B 96, 064115, 2017
Ati, M.; Enachescu, C.; Bouamrane R. Langevin dynamics simulation of a one-dimensional linear spin chain with long-range interactions, THE EUROPEAN PHYSICAL JOURNAL B, 90, 133, 2017
Gaina, R.; Enachescu, C. Nucleation in spin transition molecular magnets: a parallel between Ising-like and mechanoelastic models,PROCEEDINGS OF THE ROMANIAN ACADEMY, Series A, Volume 18, Number 3/2017, pp. 215–222
Conferences
Cristian Enachescu The mechanoelastic model for spin transition molecular magnets – Euro Asian Conference on magnetism, Krasnoyarsk, Rusia, august 2016 (oral)
Cristian Enachescu Spin crossover molecular magnets: premises for fully optical memories – International Conference of magnetic materials and new technologies, Listvyanka, Rusia, august 2016 (oral)
Cristian Enachescu, Radu Tanasa, Laurentiu Stoleriu, Alexandru Stancu, Antoine Tissot, Jérôme Laisney, Marie-Laure Boillot High spin- low spin relaxation of spin-crossover microparticles modulated by the environment. Theoretical and experimental investigations – GDR Magnetisme et commutation moleculaire, Dourdan Franța, noiembrie 2016 (oral)
Cristian Enachescu, Andreas Hauser, Marie-Laure Boillot, Maciej Lorenc, Eric Collet Understanding experimental data in spin crossover systems using elastic models – Phase Transition and Dynamical properties of Spin Transition Materials, Gandia, Spania, 2016 (Invitat)
Cristian Enăchescu, Understanding experimental data in spin crossover systems using elastic models, European Conference on Molecular Magnetism, August 2017, Bucharest, Romania (oral)
Cristian Enăchescu, Spin crossover molecular magnets micro and nanoparticles. Theoretical and experimental investigations, Second International Workshop Novel Trends in Physics of Ferroics, July 2017, Sankt Petersburg, Russia (oral)
Press releases
http://m.hotnews.ro/stire/20987751
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Exploiting porosity in ferroelectric materials by local field engineering towards improved functional properties
Financed by the Romanian National Authority for Scientific Research, CNCS – UEFISCDI,
project PN-II-RU-TE-2014, no. 257 / 2015
Project Director: dr. Leontin PADURARIU
(Faculty of Physics, Alexandru Ioan Cuza University, Iași)
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Ferroelectric-based composites are considered a better alternative to single phase ferroelectrics to accomplish the technological requirements for many applications in microelectronics. The electrical properties of such systems are governed by the inhomogeneity of the local electric field introduced by the interfaces between phases with different local permittivity. Among ferroelectric-based composites, in porous ferroelectric ceramics the local field inhomogeneity effect is maximized due to the huge permittivity contrast (1 for pores and thousands for bulk). Although porosity was generally considered undesired in ferroelectrics because is usually detrimental from functional properties point of view, when is not controlled, recent reports showed enhancement of some properties, which make very appealing a study aimed to a deeper understanding of porosity in electroceramics properties. Therefore, by local field engineering through microstructural control, porous ferroelectric present a great potential to accomplish the desired electrical properties in microelectronics. In the present project, by a multidisciplinary approach of modeling, preparation and electrical characterization, we propose to demonstrate the usefulness of local field engineering approach combined with advanced preparation methods for controlling the microstructures, in order to exploit porosity as a new tool for improving some specific functional properties of ferroelectrics
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| Dr. Leontin Padurariu | Project Manager |
| Prof. Dr. Liliana Mitoseriu | Senior Researcher |
| Dr. Lavinia Curecheriu | Postdoctoral Researcher |
| Dr. Mirela Airimioaei | Postdoctoral Researcher |
| Dr. Cristina Ciomaga | Postdoctoral Researcher |
| Roxana Patru | PhD. Student |
| Cipriana Padurariu | PhD. Student |
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The major objective of the project is to investigate by a complex modeling/experimental approach the role of porosity at various length scales and for different pore shapes on the functional properties of ferroelectric materials.
Specific objectives:
OI: Study of the role of porosity on tunability in porous paraelectric materials. Different types of porous materials will be described by modeling tools and the best configurations will be produced, experimentally investigated and compared to the modeling results:
OI.1 Modeling the tunability properties of porous ferroelectrics,
OI.2 Experimental study of the role of porosity on the low and high field properties of porous ferroelectrics in paraelectric state (e.g. BST, BZT, PMN ).
The expected scientific impact is related to: development of original multiscale models based on 3D FEM (at microscale level) and LGD theory (at mesoscale level), to describe the role of the microstructures on the nonlinear dielectric properties of porous ferroelectrics; understanding the relation between the porosity and effective properties through local field distortion at mesoscale. Novelty: a new approach in controlling the tunability properties by local field engineering and porosity control.
OII: Study of the role of porosity on the switching properties of porous ferroelectrics. The role of porosity on the switching properties at different length scales from nanoscale (lower than domain size) to microscale (larger than domain size) and various microstructures will be simulated by a complex multiscale approach (Monte Carlo and Preisach models to describe domain structures and switching properties at mesoscale and 3D FEM to describe local field inhomogeneity). The most interesting configurations will be selected to be produced, investigated and compared with simulations results:
OII.1 Modeling of the role of porosity on the switching properties of porous ferroelectrics.
OII.2 Experimental verification for porous ferroelectric ceramics (e.g. PZT, PMN-PT, BT) with different sizes and shapes of the pores.
The expected scientific impact: the contribution to understand the role of porosity on the properties of ferroelectrics at different length scales: domain structures, local hysteretic responses at mesoscale and macroscopic effective dielectric and ferroelectric properties.
OIII. Managerial objective. This objective includes: coordination of the research activity, dissemination activity (preparation and publication of ISI papers, presentations at international conferences, web-site, yearly scientific reports), acquisition of equipments and materials, etc.
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Reports:
2015 (in Romanian) (in English)
2016 (in Romanian)
2017(in Romanian)
Papers:
1. Comment on “The Impact of Composite Effect on Dielectric Constant and Tunability in Ferroelectric-Dielectric System”, L. Padurariu and L. Mitoseriu, J. Am. Ceram. Soc., 99 [11] 3816–3817 (2016) (Impact Factor =2.787)
2. Porosity-Dependent Properties of Nb-Doped Pb(Zr,Ti)O3 Ceramics, F. Gheorghiu, L. Padurariu, M. Airimioaei, L. Curecheriu, C. Ciomaga, C. Padurariu, C. Galassi, and L. Mitoseriu, J. Am. Ceram. Soc., 1–9 (2016) (Impact Factor =2. 787)
3. Role of the pore interconnectivity on the dielectric, switching and tunability properties of PZT ceramics, C. Padurariu, L. Padurariu, L. Curecheriu, C. Ciomaga, N. Horchidan, C. Galassi and L. Mitoseriu, Ceramics International, in press (Impact factor =2.758)
4. . Porous (Ba,Sr)TiO3 ceramics for tailoring dielectric and tunability properties: Modeling and experiment, R. E. Stanculescu, N. Horchidan, C. Galassi, M. Asandulesa, L. Padurariu, C. E. Ciomaga, and L. Mitoseriu, Processing and Application of Ceramics, in press (2017) (Impact factor =1.070)..
Conferences:
- Modeling of the nonlinear dielectric properties of paraelectric-dielectric composites by a 3D Finite Element Method based on Landau-Devonshire theory, L. Padurariu, L. Mitoseriu, ElectroCeramics XV, 27-29 June 2016, Limonges, France (invited presentation)
- Effect of porosity on ferroelectric-relaxor crossover in BaTiO3-based ceramics, L. Curecheriu, L. Padurariu, M.T. Buscaglia, V. Buscaglia, L. Mitoseriu, ElectroCeramics XV, 27-29 June 2016, Limonges, France (oral presentation)
- Modeling of the nonlinear dielectric properties of paraelectric-dielectric composites by a 3D Finite Element Method based on Landau-Devonshire theory, L. Padurariu, L. Mitoseriu, ISAF/ECAPD/PFM Conference in Darmstadt, 21-25 August 2016 Germany (oral presentation)
- Exploiting porosity for design tunable materials, L. Curecheriu, C. Padurariu, L. Padurariu, L. Mitoseriu, ISAF/ECAPD/PFM Conference in Darmstadt, 21-25 August 2016 Germany (oral presentation)
- Modeling of the dielectric properties of porous ferroelectric structures, L. Padurariu, L. Curecheriu, R. Stanculescu, C. Ciomaga, C. Padurariu, C. Galassi and L. Mitoseriu, IC1208 Joint 8th Management Committee Meeting (MCM8) Meetings of Working Groups WG1–WG4, 8th-9th September 2016, Warsaw, Poland (oral presentation)
- Tuning properties in electroceramics by composition and microstructural control, L.P. Curecheriu, L. Padurariu, L. Mitoseriu, COST Meeting IC1208 University of Luxembourg, March 16-17, 2017, Luxembourg (oral presentation)
- Microstructure effects on low and high field dielectric properties of (Ba,Sr)TiO3 based porous solid solutions, R. Stanculescu, N. Horchidan, L. Padurariu, C. Galassi, M. Asandulesa, C.E. Ciomaga, and L. Mitoseriu, ECerS 2017 15th Conference &Exhibition of European Ceramic Society July 9-13, 2017, Budapest, Hungary (poster presentation)
- Local field engineering for tailoring electrical properties in ferroelectric-based composites, L. Padurariu, L. Mitoseriu, ECerS 2017 15th Conference &Exhibition of European Ceramic Society July 9-13, 2017, Budapest, Hungary (invited presentation)
- Effect of porosity on the dielectric, switching and DC-tunability properties of BaTiO3 ceramics, L.P. Curecheriu, C. Padurariu, L. Padurariu, R. Stanculescu, N. Horchidan, C. Ciomaga, L. Mitoseriu, ECerS 2017 15th Conference &Exhibition of European Ceramic Society July 9-13, 2017, Budapest, Hungary (oral presentation)
- Dielectric properties of porous ferroelectric structures: modeling and experimental verification, L. Curecheriu, L. Padurariu, C. Ciomaga, R. Stanculescu, C. Padurariu, M. Airimioaei, L. Mitoseriu, IEEE ROMSC 2017 14th edition, “Alexandru Ioan Cuza” University of Iasi, Romania, 26th of June 2017 Iasi, Romania (oral presentation)
- Effect of porosity on the dielectric and dc-tunability properties of BaTiO3 ceramics, L.P. Curecheriu, C. Padurariu, L. Padurariu, R. Stanculescu, C. Ciomaga and L. Mitoseriu, 11 th International Conference PROCESSES IN ISOTOPES AND MOLECULES, 27 - 29 September 2017, Cluj-Napoca, Romania (oral presentation)
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Hysteresis and switching in exotic nano and molecular magnetic structures
(185/2011-10-05 cod proiect: PN-II-ID-PCE-2011-3-0794)
The project EXOTIC is dedicated to the study of a new class of magnetic nanostructures that can be included in the category of metamaterials. The best example of such structure is the system of artificial frustrated magnets in which, as the name suggests, the interactions between the nanomagnets are frustrated and the system can have a number of equivalent states with a certain probability. this „quantum-like” behavior is now intensively studied but the domain is still in the early stages.