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Suspenzije magnetnih nanoploščic v holesteričnih tekočih kristalih
ID Medle Rupnik, Peter (Author), ID Mertelj, Alenka (Mentor) More about this mentor... This link opens in a new window

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Abstract
Tekoči kristali so dobro poznani po tem, da se dobro odzivajo na zunanje električno polje. Ta odziv je tipično neodvisen od predznaka električnega polja. V suspenzijah magnetnih nanoploščic v tekočekristalnem mediju je po drugi strani mogoče doseči spontano magnetno ureditev, tako da je odziv na magnetno polje linearen. V tem primeru je mogoče z majhnimi magnetnimi polji kontrolirati strukture v materialu, ki ga v našem primeru zapremo v tanko urejeno plast. Z izbiro kiralnega tekočekristalnega medija (holesterični tekoči kristal) pridobimo še bolj zanimiv material. Zvito osnovno stanje holesterika namreč tekmuje s homogenimi zunanjimi polji in robnimi pogoji na mejah tanke plasti. Izkaže se, da je mogoče s kombinacijo zunanjega električnega in magnetnega polja stabilizirati vrsto kompleksnih polarnih struktur. Poleg tega dinamični odziv v tem primeru ni več invarianten na predznak zunanjega električnega polja v primeru, da je vklopljeno tudi zunanje magnetno polje. Slednje je posledica zlomov simetrij zaradi kiralnosti tekočekristalnega medija in spontane magnetizacije. V tem delu je opisanih več značilnosti tega materiala, hkrati pa so predstavljene študije morfologije in dinamike feromagnetnega holesteričnega tekočega kristala zaprtega v tanko urejeno plast.

Language:Slovenian
Keywords:tekoči kristali, feromagnetni tekoči kristali, holesterični tekoči kristali, feromagnetizem, nematodinamika, hidrodinamika, kiralnost
Work type:Master's thesis/paper
Typology:2.09 - Master's Thesis
Organization:FMF - Faculty of Mathematics and Physics
Year:2021
PID:20.500.12556/RUL-130947 This link opens in a new window
COBISS.SI-ID:77424387 This link opens in a new window
Publication date in RUL:19.09.2021
Views:1402
Downloads:118
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Secondary language

Language:English
Title:Suspensions of magnetic nanoplatelets in cholesteric liquid crystals
Abstract:
Liquid crystals are well-known for their strong response to the external electric field. This response however is typically independent of the sign of external electric field. Suspensions of magnetic nanoplatelets in liquid crystal media on the other hand exhibit spontaneous magnetic ordering and thus respond linearly to the external magnetic field. Hence moderate magnetic fields can be used to control the structure of the material, which is in our case confined to a thin ordered layer. If the chosen liquid crystal media is chiral (cholesteric liquid crystals), the resulting material is even more interesting. Wound cholesteric ground state competes with homogeneous external aligning fields and boundary conditions on the layer borders. It turns out that many complex polar structures can be stabilised with the combination of external electric and magnetic fields. Additionally, the dynamic is in this case no longer invariant to the sign of electric field, when the external magnetic field is simultaneously applied. This is a consequence of the specific symmetry breakings due to the chirality of cholesteric liquid crystals and spontaneous magnetisation. Here, several features of this material are described and experiments examining the morphology and dynamics are presented.

Keywords:liquid crystals, ferromagnetic liquid crystals, cholesteric liquid crystals, ferromagnetism, nematodynamics, hydrodynamics, chirality

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