Solid State Phenomena Vol. 190

Abstract: The motion of a thin rod with viscoelastic magnetizable material in a channelunder the action of the alternating magnetic field of the coils is considered experimentally andtheoretically. The dynamic 2D model of a thin rod with viscoelastic magnetizable material isused. Numerical calculations of the rod motion in a vertical plane under the action of alternatingmagnetic field, gravity and friction are performed using this model. An influence of parametersof the problem on the rod velocity is studied theoretically. Theoretical results are comparedwith experimental data.

Abstract: Complexes of bivalent and trivalent iron with ligands based on benzimidazole derivatives have been synthesized and investigated. Chloride-ion was used as anion. Samples ligands differed from each other in the length of alkyl radical. Some samples were found in a mix-valence state, that complicated spin transition observation. Combination of Mossbauer spectroscopy and magnetic moment in high field (15kOe) measurements in the temperatures range 130K - 350K allowed us to establish the valence of iron ions under spin transition in our samples and spin transition temperature frameworks for these mix-valence compounds.

Abstract: Several species of magntic hydrogels (ferrogels) are prepared, and their magnetic and magnetoelastic properties are examined. Three substance are used as the bases: agarose, polyacrylamide and Pluronic. All the gel matrices are filled with the same nanopowder: iron particles with the mean size about 30 nm. The critical concentrations of the magnetic phase, above which the normal gel networks cease to form, are estimated. The magnetization curves of the samples are measured at different stages of de-swelling, and their elastic properties are tested under a uniform magnetic field. The results indicate field-induced rigidity of magnetic hydrogels

Abstract: The structure properties of magnetic fluids are studied in the absence of an external magnetic field focusing the main attention on the influence of ferroparticle polydispersity. Magnetic fluid is modeled by a bidisperse system of uniformly magnetized hard spherical particles with permanent magnetic moments. The magnetic fluid microstructure is described with the help of the pair correlation function, and the ferroparticle polydispersity is taken into account within the bounds of bidisperse system. For the parameters, which are typical for real commercial magnetic fluids, we have obtained that the majority of ferroparticles (small is sizes) are less correlated. At the same time the large particles, which are small in number, are strongly correlated.

Abstract: Results on anisotropic magnetorheological elastomers magnetoelasticity are presented and discussed. In the dipole approximation, and considering the MRE as a continuous linear body, the effects of magnetic field on its main elastic properties (linear deformations and Young module) are investigated. Experimental evidences that the compression of the cylindrical bar is influenced by the intensity of the longitudinal magnetic field and the Young module of the MRE sample increases with the intensity H of the longitudinal magnetic field are obtained and the results discussed.

Abstract: Tests have been carried out to measure the temperature dependence of static susceptibility of a magnetic fluid stabilized with polypropylene glycol (PPG) in propanol, ethyl ether and propylene oxide. The use of propylene oxide provides the widest temperature range for measurements of fluid susceptibility. The coagulation stability of the PPG-stabilized magnetic fluid against ethylene glycol and 1,4-butylene glycol is investigated. It has been shown that ethylene glycol can be used to separate PPG magnetic fluid into fractions. The fluid separation begins as soon as the volumetric fraction of ethylene glycol exceeds 30%. Butylene glycol is unsuitable for fractionation but can be used to remove excess surfactant - PPG.

Abstract: The dynamics of a microdrop of dielectric liquid suspended in a magnetic fluid under the action of electric and magnetic fields is studied experimentally. With increasing electric field, the deformation of droplets into oblate spheroid, toroid and curved toroid was observed. At the further increase in the electric field, the bursting of droplets and electrorotation were also investigated. The influence of an additional magnetic field on the droplet dynamics was studied.

Abstract: The influence of the inertial effects on the non-equilibrium magnetization of a suspensionof Brownian magnetic particles in a viscous liquid in a varying uniform magnetic field is theoreticallystudied. Themagnetization of the suspension is calculated. The heat generation power density is foundas a function of the frequency of the applied magnetic field.

Abstract: The effect of point lattice defects on the magnetic properties of manganites LaMnO_3+δ, La_0.67Ca_0.33MnO₃ and La_0.67Ba_0.33MnO₃ has been investigated. Temperature dependences of magnetic susceptibility of the initial and electron-irradiated (F9×1018 e/cm²) samples were measured in the temperature range 80K

Abstract: Effect of the partial oxygen isotope substitution on (Pr_1-yEu_y)_0.7Ca_0.3CoO₃ cobaltites was studied in detail for the crossover region (0.12<у<0.26) of the phase diagram. We prepared a series of the cobaltite samples with the different degrees of enrichment by the heavy oxygen isotope ¹⁸O, namely, containing 90%, 67%, 43%, 17%, and 0% of ¹⁸O. The Eu doping of the samples was chosen to be near and on the both sides of the crossover doping level y_cr. Based on measurements of the ac magnetic susceptibility χ(Т) and electrical resistivity ρ(Т), we were able to analyze the evolution the sample properties with the change Eu and ¹⁸O content.