Magnetic sensitivity of a dispersion of aggregated ferromagnetic carbon nanotubes in liquid crystals

Buluy, O.; Nepijko, S. A.; Reshetnyak, Victor; Ouskova, E.; Zadorozhnii, V.I.; Leonhardt, A.; Ritschel, M.; Schönhense, G.; Reznikov, Yuriy

doi:10.1039/c0sm00131g

Cited by 100 publications

(55 citation statements)

References 28 publications

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“…Our experimental results, on the one hand, are in agreement with the recent reports [9,10], regarding the dependence of the effect on the concentration and type of nanoparticles. On the other hand, our measurements indicate that the aligning bias magnetic field (used in Refs.…”

Section: Resultssupporting

confidence: 82%

“…In recent works by Podoliak et al [9], and Buluy et al [10] both experimental and theoretical investigations have been reported about the optical response of suspensions of ferromagnetic nanoparticles in nematic liquid crystals on the imposed magnetic field (which finally leads to a Fréedericksz transition). The authors have measured an additional, linear response in ferronematics at low magnetic fields (far below B F ).…”

Section: Introductionmentioning

confidence: 99%

“…We have to note here that in Refs. [9,10] a weak bias magnetic field (B bias ≈ 2 mT) has also been applied parallel to n in order to align the magnetic dipole moments of the nanoparticles parallel with n as an initial condition. • and 3…”

Section: Introductionmentioning

confidence: 99%

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Capacitance changes in ferronematic liquid crystals induced by low magnetic fields

et al. 2013

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The response in capacitance to low external magnetic fields (up to 0.1 T) of suspensions of spherical magnetic nanoparticles, single-wall carbon nanotubes (SWCNT), SWCNT functionalized with carboxyl group (SWCNT-COOH) and SWCNT functionalized with Fe 3 O 4 nanoparticles in a nematic liquid crystal has been studied experimentally. The volume concentration of nanoparticles was φ 1 = 10 −4 and φ 2 = 10 −3 . Independent of the type and the volume concentration of the nanoparticles, a linear response to low magnetic fields (far below the magnetic Fréederiksz transition threshold) has been observed, which is not present in the undoped nematic.

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Section: Resultssupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

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Capacitance changes in ferronematic liquid crystals induced by low magnetic fields

et al. 2013

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“…After the first experimental realization [2], the idea has been extensively tested in ferronematic suspensions of various compositions -see e.g., [3,4,5], review articles [6,7], and references therein. During these experiments an important difficulty has arisen: the aggregation of the nanoparticles [8].…”

Section: Introductionmentioning

confidence: 99%

High concentration ferronematics in low magnetic fields

Tóth-Katona

Szűcs

Éber

et al. 2014

Journal of Magnetism and Magnetic Materials

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We investigated experimentally the magneto-optical and dielectric properties of magnetic-nanoparticle-doped nematic liquid crystals (ferronematics). Our studies focus on the effect of the very small orienting bias magnetic field B bias , and that of the nematic director pretilt at the boundary surfaces in our systems sensitive to low magnetic fields. Based on the results we assert that B bias is not necessarily required for a detectable response to low magnetic fields, and that the initial pretilt, as well as the aggregation of the nanoparticles play an important (though not yet explored enough) role.

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“…Whereas the field sensitivity has been investigated and verified in many experiments [2][3][4][5][6][7][8], new interest was stimulated by the recent discovery of spontaneous magnetic ordering in a hybrid system of large, micron-sized magnetic plates embedded in a lyotropic nematic LC [9]. A crucial ingredient for the observed behavior are the LCmediated interactions stemming from local distortions of the LC director via the presence of the plates, whose size is much larger than that of the LC molecules.…”

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confidence: 99%

Spontaneous ordering of magnetic particles in liquid crystals: From chains to biaxial lamellae

Peroukidis

Klapp

2015

Phys. Rev. E

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Using Monte Carlo (MC) computer simulations we explore the self-assembly and ordering behavior of a hybrid, soft magnetic system consisting of small magnetic nano-spheres in a liquid-crystalline (LC) matrix. Inspired by recent experiments with colloidal rod-matrices we focus on conditions where the sphere and rod diameters are comparable. Already in the absence of a magnetic field, the nematic ordering of the LC can stabilize formation of magnetic chains along the nematic or smectic director, yielding a state with local (yet no macroscopic) magnetic order. The chains, in turn, increase the overall nematic order, reflecting the complex interplay of the structure formation of the two components. Increasing the sphere diameter the spontaneous uniaxial ordering is replaced by biaxial lamellar morphologies characterized by alternating layers of rods and magnetic chains oriented perpendicular to the rod's director. These novel ordering scenarios at zero field suggest complex response of the resulting hybrid to external stimuli such as magnetic fields and shear forces.Mixtures of magnetic nanoparticles (MNP) in liquidcrystalline (LC) matrices attract attention in fundamental physics and material science since about four decades ago: in 1970, Brochard and de Gennes [1] predicted, based on free energy considerations, various new effects including spontaneous magnetization in the liquid state, "compensated" phases and giant field-induced effects. Whereas the field sensitivity has been investigated and verified in many experiments [2][3][4][5][6][7][8], new interest was stimulated by the recent discovery of spontaneous magnetic ordering in a hybrid system of large, micron-sized magnetic plates embedded in a lyotropic nematic LC [9]. A crucial ingredient for the observed behavior are the LCmediated interactions stemming from local distortions of the LC director via the presence of the plates, whose size is much larger than that of the LC molecules. Indeed, LC-mediated elastic interactions and their consequences for colloidal self-assembly and ordering have intensively studied by experiments [10] and simulations [11,12] for many (non-magnetic) colloid/LC mixtures.In the present letter we focus on the opposite case of small MNPs in LC matrices, where the sizes are comparable and distortions of the LC do not play a significant role. An example of such systems are lyotropic suspensions of colloid pigment rods and magnetite MNPs which have been recently studied to investigate field-induced ordering effects [13, 14]. However, although there is strong interest in using such hybrids as new, stimuli-responsive or even adaptive materials [9], the microscopic structure of small MNPs in LC matrices is essentially unexplored; although this is clearly a prerequisite in terms of advancing new functionalities. Experimentally, the challenge is to actually "see" the relatively small MNPs with typical diameters of 10-15 nm; a solution of this problem might be provided by recently developed tomography techniques [15]. Suprisingly, however, the...

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Magnetic sensitivity of a dispersion of aggregated ferromagnetic carbon nanotubes in liquid crystals

Cited by 100 publications

References 28 publications

Capacitance changes in ferronematic liquid crystals induced by low magnetic fields

Capacitance changes in ferronematic liquid crystals induced by low magnetic fields

High concentration ferronematics in low magnetic fields

Spontaneous ordering of magnetic particles in liquid crystals: From chains to biaxial lamellae

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