Effect of Liquid Crystalline Host on Structural Changes in Magnetosomes Based Ferronematics

Abstract

The effect of the liquid crystalline host on structural changes in magnetosomes based on ferronematics is studied using the surface acoustic wave (SAW) technique supported by some capacitance and light transmission measurements. The measurement of the attenuation response of SAW propagating along the interface between LC and the piezoelectric substrate is used to study processes of structural changes under magnetic field. The magnetosome nanoparticles of the same volume concentration were added to three different nematic LCs, 5CB, 6CB, and E7. Unlike to undoped LCs, the different responses of SAW attenuation under the influence of magnetic and electric fields in LCs doped with magnetosomes were observed due to characteristic structural changes. The decrease of the threshold field for doped LCs as compared with pure LCs and slight effects on structural changes were registered. The threshold magnetic fields of LCs and composites were determined from capacitance measurements, and the slight shift to lower values was registered for doped LCs. The shift of nematic-isotropic transition was registered from dependencies of SAW attenuation on temperature. The acoustic anisotropy measurement approved the previous supposition about the role of bulk viscosity in used SAW measurements. In addition, capacitance and light transmition investigations supported SAW results and pointed out conclusions about their magnetic field behavior. Obtained results are discussed and confronted with previous ones and coincide well with those observed using acoustic, optical, or dielectric techniques.

The Role of Diamonds Dispersed in Ferronematic Liquid Crystals on Structural Properties

“…The prepared LC (5CB) composites are investigated with the main intention being to determine the effect of DNPs on structural changes under an external magnetic field, including their effect on the threshold field shift and transition temperatures for individual LC composites. The connection of the utilized experimental techniques, the results of which we report here, provided interesting results in the last decade [20][21][22].…”

Study on the Memory Effect in Aerosil-Filled Nematic Liquid Crystal Doped with Magnetic Nanoparticles

“…The intensity of transmitted light was registered with a photodetector and subsequently recorded by a computer as the light transmission dependence on electric or magnetic fields. The complete experimental arrangement configuration was already described in [33,34]. The light transmission in the case of parallel polarizers was then expressed as I/I 0 , and in the case of crossed polarizers, as (I − I 0 )/I 0 , where I was the measured light intensity and I 0 was the maximal intensity of incident light passing through the LC.…”

“…Results reported here were obtained for the first time using both light transmission measurements and surface acoustic wave (SAW) attenuation response measurements. The connection between these techniques has provided interesting results in the last decade [33][34][35].…”

Ferronematic Co(II) Complex: An Active Filler for Magnetically Actuated Soft Materials

“…[4][5][6] Nevertheless, De Gennes and Brochard proposed that by coupling the magnetic moment of metal nanoparticles and the orientational order of the nematics, the magnetic response of LCs can be improved. [7][8][9] Since then, many nematics were doped mainly with Fe 3 O 4 , [10] or other magnetic compounds, such as [Fe(acac) 3 ], barium hexaferrite (BaFe 12 O 19 ), and Co[N(SiMe3) 2 ] 2 , [11][12][13][14][15] and, as a consequence, many ferronematics that respond at low-intensity magnetic fields (e.g., 1mT) were reported. [16] Nonetheless, many of those systems are difficult to stabilize due to the phase separation, inhomogeneously space arrangement of LCs, or the specific conditions for coupling the magnetic moment with the orientational order (e.g., shape, anisotropy, anchoring energy, and nanoparticle size).…”