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A procedure of magnetophoretic investigation of low-magnetic microparticles sedimenting in a fluid under the action of the inhomogeneous magnetic field of two saturation-magnetizable rectangular ferromagnetic rods has been substantiated theoretically. The results of experimental investigation of the magnetic susceptibility of micrometer para-and diamagnetic particles have been presented. Introduction.In the mid-1970s, the method of magnetic separation attracted attention in many spheres of activity, including water purification and gas scrubbing, clay cleaning, chemical technologies, medicine, and biology [1][2][3][4][5][6][7]. Using a magnetic field combining a high strength and a strong small-scale inhomogeneity, one can isolate even very small low-magnetic objects, including particles of cellular suspensions from a gas or fluid flow. High-gradient magnetic filters are traditionally created by application of a homogeneous magnetic field to a volume in which small ferromagnetic bodies are distributed. The finer the particles isolated and the weaker their magnetic properties, the stronger must be the external field and the smaller the dimensions of the elements of a ferromagnetic head. Thus, to isolate red blood cells one uses bundles of ferromagnetic wire about 100 µm in diameter [2,5]. In flow systems, the efficiency of such a filter structure is low, since the probability of the particle being captured is low and decreases with increase in the pumping rate. Fundamentally new possibilities are offered by the concept of high-gradient magnetic separation on coherent (ordered) magnetic structures [8][9][10][11]. The order of a magnetic structure creates prerequisities for a sharp improvement in the properties of a filter by accumulation of the effect of magnetophoretic displacement of the particles isolated in the process of motion of the suspension. Furthermore, periodic structures allow detailed description of the distribution of a magnetic field in them, thus offering possibilities of using mathematical optimization methods. Practical development of an optimum system requires, among other things, data on the magnetic properties of the particles being separated. In many cases, particularly when we are dealing with cellular suspensions, this information is lacking. In such a situation, to measure the magnetic susceptibility of particles, one can use magnetophoretic experiments in which the susceptibility is determined from the particle velocity in a prescribed inhomogeneous field, usually in the field of a ferromagnetic cylinder [12]. Measurements in the cylinder's field are rather difficult, since the particle moves in three directions. In the present work, we have considered and used in practice a more practical magnetophoretic procedure for studying the susceptibility of dia-and paramagnetic microparticles.Theoretical Prerequisites. The geometry of the magnetophoretic cell in question is shown in Fig. 1. The cell (Fig. 1a) includes a vertical rectangular channel 1 whose horizontal cross section has width 2W an...

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