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Abstract
During hydrothermal synthesis the magnetoplumbite strontium-ferrite nanoplatelets form via the growth of primary discoid nanoplatelets with a new, incredibly complex hexagonal structure.
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Affiliation(s)
- D. Makovec
- Department for Materials Synthesis
- Jožef Stefan Institute
- SI-1000 Ljubljana
- Slovenia
| | - G. Dražić
- Department for Materials Chemistry
- National Institute of Chemistry
- SI-1000 Ljubljana
- Slovenia
| | - S. Gyergyek
- Department for Materials Synthesis
- Jožef Stefan Institute
- SI-1000 Ljubljana
- Slovenia
| | - D. Lisjak
- Department for Materials Synthesis
- Jožef Stefan Institute
- SI-1000 Ljubljana
- Slovenia
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2
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Gao S, Fleisch M, Rupp RA, Cmok L, Medle-Rupnik P, Mertelj A, Lisjak D, Zhang X, Drevenšek-Olenik I. Magnetically tunable optical diffraction gratings based on a ferromagnetic liquid crystal. Opt Express 2019; 27:8900-8911. [PMID: 31052701 DOI: 10.1364/oe.27.008900] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Accepted: 02/13/2019] [Indexed: 06/09/2023]
Abstract
Transmission optical diffraction gratings composed of periodic slices of a ferromagnetic liquid crystal and a conventional photoresist polymer are demonstrated. Dependence of diffraction efficiencies of various diffraction orders on an in-plane external magnetic field is investigated. It is shown that diffraction properties can be effectively tuned by magnetic fields as low as a few mT. The tuning mechanism is explained in the framework of a simple empirical model and also by numerical simulations based on the rigorous coupled wave analysis (RCWA). The obtained results provide a proof of principle of operation of magnetically tunable liquid crystalline diffractive optical elements applicable in contactless schemes for control of optical signals.
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Sebastian N, Lisjak D, Čopič M, Buchnev O, Mertelj A. Comparison of dynamic behavior of ferroelectric and ferromagnetic nematic suspensions. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2017.11.157] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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4
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Makovec D, Belec B, Goršak T, Lisjak D, Komelj M, DraŽić G, Gyergyek S. Discrete evolution of the crystal structure during the growth of Ba-hexaferrite nanoplatelets. Nanoscale 2018; 10:14480-14491. [PMID: 30022216 DOI: 10.1039/c8nr03815e] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
An understanding of the adaptation of the crystal structure of materials confined at the nanoscale, the influences of their specific structures on the evolution of their morphologies and, finally, their functional properties is essential not only for expanding fundamental knowledge, but also for facilitating the designs of novel nanostructures for diverse technological and medical applications. Here we describe how the distinct structure of barium-hexaferrite nanoplatelets evolves in a stepwise manner in parallel with the development of their size and morphology during hydrothermal synthesis. The nanoplatelets are formed by reactions between Ba- and Fe-hydroxides in an aqueous suspension at temperatures below 80 °C. Scanning-transmission electron microscopy showed that the structure of the as-synthesized, discoid nanoplatelets (∼2.3 nm thick, ∼10 nm wide) terminates at the basal surfaces with Ba-containing planes. However, after subsequent washing of the nanoplatelets with water the top two atomic layers dissolve from the surfaces. The final structure can be represented by a SRS* sequence of the barium-hexaferrite SRS*R* unit cell, where S and R represent a hexagonal (BaFe6O11)2- and a cubic (Fe6O8)2+ structural block, respectively. Due to the stable SRS* structure, the thickness of the primary nanoplatelets remains unchanged up to approximately 150 °C, when some of the primary nanoplatelets start to grow exaggeratedly and their thicknesses increase discretely with the addition of the RS segments to their structure. The SRS* structure of the primary nanoplatelets is too thin for the complete development of magnetic ordering. However, the addition of just one RS segment (SRS*R*S structure) gives the nanoplatelets hard magnetic properties.
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Affiliation(s)
- D Makovec
- Department for Materials Synthesis, JoŽef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
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5
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Shuai M, Klittnick A, Shen Y, Smith GP, Tuchband MR, Zhu C, Petschek RG, Mertelj A, Lisjak D, Čopič M, Maclennan JE, Glaser MA, Clark NA. Spontaneous liquid crystal and ferromagnetic ordering of colloidal magnetic nanoplates. Nat Commun 2016; 7:10394. [PMID: 26817823 PMCID: PMC4738347 DOI: 10.1038/ncomms10394] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 12/08/2015] [Indexed: 11/18/2022] Open
Abstract
Ferrofluids are familiar as colloidal suspensions of ferromagnetic nanoparticles in aqueous or organic solvents. The dispersed particles are randomly oriented but their moments become aligned if a magnetic field is applied, producing a variety of exotic and useful magnetomechanical effects. A longstanding interest and challenge has been to make such suspensions macroscopically ferromagnetic, that is having uniform magnetic alignment in the absence of a field. Here we report a fluid suspension of magnetic nanoplates that spontaneously aligns into an equilibrium nematic liquid crystal phase that is also macroscopically ferromagnetic. Its zero-field magnetization produces distinctive magnetic self-interaction effects, including liquid crystal textures of fluid block domains arranged in closed flux loops, and makes this phase highly sensitive, with it dramatically changing shape even in the Earth's magnetic field. Ferromagnetism has been known as a material property of solids since the time of the ancient Greeks. Here, Shuai et al. report that magnetic nanoplates suspended in a simple solvent can spontaneously align to form a ferromagnetic liquid, capable of both producing and sensing magnetic fields.
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Affiliation(s)
- M Shuai
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - A Klittnick
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - Y Shen
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - G P Smith
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - M R Tuchband
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - C Zhu
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - R G Petschek
- Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - A Mertelj
- Jozef Stefan Institute, SI-1000 Ljubljana, Slovenia
| | - D Lisjak
- Jozef Stefan Institute, SI-1000 Ljubljana, Slovenia
| | - M Čopič
- Jozef Stefan Institute, SI-1000 Ljubljana, Slovenia.,Faculty of Mathematics and Physics, University of Ljubljana, SI-1000 Ljubljana, Slovenia
| | - J E Maclennan
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - M A Glaser
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
| | - N A Clark
- Department of Physics and Soft Materials Research Center, University of Colorado, Boulder, Colorado 80309, USA
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6
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Abstract
The partial dissolution of selected nanoparticles (NaYF4, LaF3 and GdF3) co-doped with Yb3+ and Tm3+ was detected and compared with respect to their size, chemical composition and structure.
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Affiliation(s)
- D. Lisjak
- Jožef Stefan Institute
- SI-1000 Ljubljana
- Slovenia
| | - O. Plohl
- Jožef Stefan Institute
- SI-1000 Ljubljana
- Slovenia
- Jožef Stefan International Postgraduate School
- SI-1000 Ljubljana
| | | | - B. Majaron
- Jožef Stefan Institute
- SI-1000 Ljubljana
- Slovenia
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7
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Primc D, Makovec D, Lisjak D, Drofenik M. Hydrothermal synthesis of ultrafine barium hexaferrite nanoparticles and the preparation of their stable suspensions. Nanotechnology 2009; 20:315605. [PMID: 19597254 DOI: 10.1088/0957-4484/20/31/315605] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The hydrothermal treatment of an appropriate suspension of Ba and Fe hydroxides in the presence of a large excess of OH(-) results in the formation of Ba hexaferrite at temperatures as low as 150 degrees C. This low formation temperature enables the synthesis of uniform, ultrafine Ba hexaferrite nanoparticles. These nanoparticles have a disc-like shape, approximately 10 nm wide, but only approximately 3 nm thick. When the temperature of the hydrothermal treatment is increased, large platelet Ba hexaferrite crystals appear as a consequence of secondary re-crystallization (Ostwald ripening). In this work, this undesired process of secondary re-crystallization has been evaluated. We show that the secondary re-crystallization can be totally suppressed with the use of an oleic acid surfactant. The addition of oleic acid enabled the synthesis of uniform, ultrafine nanoparticles at temperatures up to 240 degrees C. The nanoparticles were hydrophobic and could be suspended in nonpolar liquids to form relatively concentrated ferrofluids. Such stable suspensions of hexaferrite nanoparticles will be technologically important, especially as precursors for the preparation of new nanostructured materials, for example nanocomposites or nanostructured ceramic films.
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Affiliation(s)
- D Primc
- Jozef Stefan Institute, Department for Material Synthesis, Ljubljana, Slovenia.
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8
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Branković D, Jokanović V, Babić-Stojić B, Jagličić Z, Lisjak D, Kojić D. Interference effect between superparamagnetic and spin glass correlated moments in a system of dispersed Co(3)O(4) nanocrystallites. J Phys Condens Matter 2009; 21:095303. [PMID: 21817386 DOI: 10.1088/0953-8984/21/9/095303] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
An inhomogeneous system of aggregates of Co(3)O(4) nanocrystallites dispersed in an amorphous SiO(2) matrix has been studied. X-ray diffraction and atomic force microscopy reveal a bimodal distribution of crystallite sizes, smaller nanocrystallites with dimension below 10 nm and larger nanocrystallites of about 20 nm. The Co(3)O(4) nanocrystallites enter the composition of nanograins with dimension 20-60 nm. The nanograins build aggregates with dimension 200-500 nm. A large value of the effective magnetic moment per Co(2+) ion obtained from the high-temperature susceptibility measurements indicates possible disturbance of the normal spinel structure in which a fraction of Co(3+) ions also possesses magnetic moment. An analysis based on the temperature dependence of the coercive field has shown that the smaller nanocrystallites behave as superparamagnetic particles with a blocking temperature of about 10 K. Simultaneous existence of two relaxation processes is observed in the frequency dependence of the imaginary part of the ac magnetic susceptibility in the vicinity of T = 15.8 K. The temperature dependence of the width of the distribution function of relaxation times obtained from the Cole-Cole diagrams exhibits behaviour characteristic for spin glass dynamics in a temperature range above 17.6 K and is temperature independent below 15.8 K, which is a property of superparamagnetic particles. The variation of the width of the distribution function between 17.6 and 15.8 K indicates that interference of the superparamagnetic and spin glass dynamics occurs. It has been found that average relaxation time increases with decreasing temperature from τ(c)<10(-4) s at 17.6 K to 1.5 × 10(-1) s at 15 K. The increase of the average relaxation time with decreasing temperature, the observed blocking temperature of the superparamagnetic moments at about 10 K and interference appearing between the two spin dynamics suggest that the magnetic moments in the smaller as well as in the larger nanocrystallites are subject to a thermally activated blocking process at low temperatures.
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Affiliation(s)
- D Branković
- Vinča Institute of Nuclear Sciences, PO Box 522, 11001 Belgrade, Serbia
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Kosovcević M, Marić D, Lisjak D, Radalović S. [Prosthetic management of non-vital teeth]. Stomatol Glas Srb 1974; 21:257-63. [PMID: 4620697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Marić D, Kosovćević M, Lisjak D, Mikić D. [Radiography in prosthodontics]. Stomatol Glas Srb 1973; 20:241-6. [PMID: 4596443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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12
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Lisjak D, Dordević D, Marinković B. [Emergencies in dental practice--their prevention and treatment]. Stomatol Glas Srb 1973; 20:187-90. [PMID: 4523221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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