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Assuming the magnetic fluid a homogeneous dipole gas implies its magnetization description by the Langevin law derived for an ensemble of molecules of paramagnetic gas. In the paper, an approach used in the literature and aimed at finding the regularities of the magnetization process of paramagnets and of the possibilities of its routine application to characterize similar processes in magnetic colloids is critically analyzed. Basing on the results of experimental studies of the temperature and concentration dependences of magnetic susceptibility, effective fields in such media have been calculated and the conditions for applying models typical of molecular paramagnets have been found. [ABSTRACT FROM AUTHOR]

An experiment on the propagation of a plane-polarized SHF-ranged electromagnetic wave in magnetic colloids containing magnetite particles was performed. It is found that the action of the magnetic field aligned with the wave on such media results in turning (rotation) of the wave polarization plane (Faraday effect). Moreover, this effect is pronounced only at exceeding a certain critical volume concentration of magnetite. Some peculiarities of the phenomenon have been found in structurally ordered magnetic colloids which could be attributed to the alteration of their structure under the magnetic field action. [ABSTRACT FROM AUTHOR]

Investigations of temperature dependences of dynamic susceptibility for three ferrofluid samples with different size distributions are presented. These studies were performed at different sampling frequencies under the action of an external DC magnetic field. Analysis was done in terms of a Debye-like theory of complex susceptibility. It was also found that the temperature corresponding to maximum of the imaginary component of the complex magnetic susceptibility depends on the frequency of the probing field as a Vogel-Fulcher-like law. [ABSTRACT FROM AUTHOR]

The paper presents results of the investigation of magnetization features of thin layers of differently based magnetic colloids with a well-developed system of magnetized aggregates, exposed to magnetic and electric fields. It has been found that the magnetization processes of volumetric samples and of thin layers differ. For thin layers of the investigated magnetic fluid, a dependence of the magnetization relaxation time on the layer thickness and also on the mutual orientation of the layer plane and external constant magnetic field is found. It is shown that an alternating electric field also affects the magnetic properties of a thin layer of magnetic colloid with magnetized aggregates. [ABSTRACT FROM AUTHOR]

Investigation results on the influence of shear flow on the magnetic susceptibility of magnetic viscous-based colloids are reported. Additional action of an external constant magnetic field has been found to cause a maximum in the dependence of magnetic susceptibility on shear rate, the position of which is determined by the magnitude and orientation of the external field. The obtained results are theoretically based on an assumption that the action of the external magnetic field initiates the formation of aggregates in an initially homogeneous magnetic colloid sample; the aggregates’ size is determined by the external field magnitude and shear rate. A mean critical number of particles in an aggregate is defined which corresponds to the magnetic susceptibility maximum for different orientations of the external magnetic field. [ABSTRACT FROM AUTHOR]

In this work, results of the studies of structural behavior of system aggregates with a nonzero magnetic moment carried out by optical methods are presented. Similar aggregates were produced by adding a solution of oleic acid in kerosene into an initially homogeneous paste-like magnetic colloid; the average size of disperse particles 20 mn. The results of the study of structures with magnetized aggregates forming in magnetic colloids under the action of an elliptically polarized rotating magnetic field are discussed. When a magnetic colloid layer with magnetized aggregates is affected by an elliptically polarized rotating magnetic field, certain ordering of the structural lattice is observed, which is determined by the frequency and orientation of the polarization ellipse of the rotating magnetic field as well as by the value of an additionally imposed steady magnetic field. It is assumed that the observed structural ordering in such systems under the action of magnetic fields of different configuration could be applicable to control the macroscopic peculiarities directly related to the character of the colloid structural order. [ABSTRACT FROM AUTHOR]

Magnetization features of thin layers of magnetic fluids with a well-developed system of magnetized aggregates have been investigated. It has been concluded that the reduction of the layer thickness results in the formation of a 2D system of magnetized aggregates that is advantageous to their orientational interaction. A possibility of aggregate spatial ordering was found under the influence of rotating and crossed steady and alternating magnetic fields. [ABSTRACT FROM AUTHOR]

Results are reported, which confirm the possibility of magnetic ordering emergence in magnetic colloids. Conditions providing the emergence of magnetized structural aggregations in the above-mentioned systems have been analyzed; results of investigations of original samples (fluids), in which they can be produced, as well as colloids with a well-developed system of magnetized aggregates are discussed. [ABSTRACT FROM AUTHOR]