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PubMed2001

On the Interfacial Deformation of a Magnetic Liquid Drop under the Simultaneous Action of Electric and Magnetic Fields.

The influence of uniform constant magnetic and electric fields, acting simultaneously, on a magnetic fluid drop is theoretically investigated. The drop is suspended in another magnetic fluid that is immiscible with the former. Both fluids are regarded as incompressible, viscous, weakly electrically conducting, polarizable, and magnetizable. The relative orientation of electric and magnetic intensity vectors is arbitrary. The equation for the surface of the drop is obtained in the approximation of small distortion of the drop. It is shown that the surface is an ellipsoid whose semiaxes can be expressed in terms of the intensity vectors of the electric and magnetic fields. The relations determining the orientation of its principal axes are also obtained. Copyright 2001 Academic Press.

Journal Article↗
PubMed2004

Functional magnetic resonance imaging (magnetization transfer) and stereological analysis of human placentae in normal pregnancy and in pre-eclampsia and intrauterine growth restriction.

Magnetic resonance imaging provides a non-invasive method for investigating functional changes in the human placenta in vivo. In this study, we combine a magnetic resonance imaging technique called magnetization transfer with established stereological methods in order to analyse and compare placentae from normal (16-36 weeks of gestation) and complicated (pre-eclampsia, intrauterine growth restriction) pregnancies. Magnetization transfer provided an in vivo measure of the ratio of bound protons:total protons and stereological analysis of histological sections was used to estimate a residual:total volume ratio (the ratio of non-vascular volume to total placental volume). Statistical comparisons were drawn using tests for related samples (longitudinal data) or one-way analysis of variance (cross-sectional data). We found no significant differences in magnetization transfer between gestational age groups or between uncomplicated pregnancies and pregnancies complicated by pre-eclampsia or intrauterine growth restriction. In comparable groups of different subjects, stereological analyses also failed to demonstrate significant differences in residual:total volume ratios. We conclude that [a] the ratio of non-vascular volume:total placental volume does not alter between 16 and 36 weeks of normal gestation, and [b] this integrated response is also conserved in pre-eclampsia and intrauterine growth restriction.

Birth Weight↗
PubMed2003

170 nm nuclear magnetic resonance imaging using magnetic resonance force microscopy.

We demonstrate one-dimensional nuclear magnetic resonance imaging of the semiconductor GaAs with 170 nm slice separation and resolve two regions of reduced nuclear spin polarization density separated by only 500 nm. This was achieved by force detection of the magnetic resonance, magnetic resonance force microscopy (MRFM), in combination with optical pumping to increase the nuclear spin polarization. Optical pumping of the GaAs created spin polarization up to 12 times larger than the thermal nuclear spin polarization at 5K and 4T. The experiment was sensitive to sample volumes of 50 microm(3) containing approximately 4 x 10(11)71 Ga/Hz. These results demonstrate the ability of force-detected magnetic resonance to apply magnetic resonance imaging to semiconductor devices and other nanostructures.

Journal Article↗
PubMed2002

Synthesis, structure, and magnetic properties of the single-molecule magnet [Ni(21)(cit)(12)(OH)(10)(H(2)O)(10)](16-).

The preparation of two new compounds containing the cluster [Ni(21)(cit)(12)(OH)(10)(H(2)O)(10)](16-) is presented, together with a detailed magnetic investigation of one of the compounds. We found that this cluster shows an unexpected stability and that it exists as different stereoisomers. Compound 1 contains the achiral cluster with a Delta-Lambda configuration, and compound 2 contains a pair of enantiomeric clusters with the configurations Delta-Delta and Lambda-Lambda, respectively. Magnetic measurements of 1 in the millikelvin range were necessary to determine the spin ground state of S = 3, and they also revealed a magnetic anisotropy within the ground state. A frequency-dependent out-of-phase signal was found in alternating current susceptibility measurements at very low temperatures, which indicates a slow relaxation of the magnetization. Thus, individual molecules are acting as single magnetic units, which is a rare phenomenon for nickel clusters. The energy barrier exhibited by compound 1 has been calculated to be 2.9 K.

Journal Article↗
PubMed2004

Synthesis, structure, and magnetic properties of a [Mn22] wheel-like single-molecule magnet.

The synthesis and magnetic properties of the compound [Mn(22)O(6)(OMe)(14)(O(2)CMe)(16)(tmp)(8)(HIm)(2)] 1 are reported. Complex 1 was prepared by treatment of [Mn(3)O(MeCO(2))(6)(HIm)(3)](MeCO(2)) (HIm = imidazole) with 1,1,1-tris(hydroxymethyl)propane (H(3)tmp) in MeOH. Complex 1.2MeOH crystallizes in the orthorhombic space group Pbca. The molecule consists of a metallic core of 2 Mn(IV), 18 Mn(III), and 2 Mn(II) ions linked by a combination of 6 micro(3)-bridging O(2)(-) ions, 14 micro(3)- and micro(2)-bridging MeO(-) ions, 16 micro-MeCO(2)(-) ligands, and 8 tmp(3)(-) ligands, which use their alkoxide arms to bridge in a variety of ways. The metal-oxygen core is best described as a wheel made from [Mn(3)O(4)] partial cubes and [Mn(3)O] triangles. Variable-temperature direct current (dc) magnetic susceptibility data were collected for complex 1 in the 1.8-300 K temperature range in a 1 T applied field. The chi(M)T value steadily decreases from 56 cm(3) K mol(-)(1) at 300 K to 48.3 cm(3) K mol(-)(1) at 30 K and then increases slightly to reach a maximum value of 48.6 cm(3) K mol(-)(1) at 15 K before dropping rapidly to 40.3 cm(3) K mol(-)(1) at 5 K. The ground-state spin of complex 1 was established by magnetization measurements in the 0.1-2.0 T and 1.80-4.00 K ranges. Fitting of the data by a matrix-diagonalization method to a model that assumes only the ground state is populated and incorporating only axial zero-field splitting (DS(z)()(2)), gave a best fit of S = 10, g = 1.96 and D = -0.10 cm(-)(1). The ac magnetization measurements performed on complex 1 in the 1.8-8 K range in a 3.5 G ac field oscillating at 50-1000 Hz showed frequency-dependent ac susceptibility signals below 3 K. Single-crystal hysteresis loop and relaxation measurements indicate loops whose coercivities are strongly temperature and time dependent, increasing with decreasing temperature and increasing field sweep rate, as expected for the superparamagnetic-like behavior of a single-molecule magnet, with a blocking temperature (T(B)) of approximately 1.3 K.

Journal Article↗
PubMed1997

A New Family of High-Dimensional Molecular Magnets Built from the Manganese-Azido System. Syntheses, Structures, and Magnetic Characterization of Two New Ferro-Antiferromagnetic Two-Dimensional Complexes.

Two new compounds in the series of general formula [Mn(L)(2)(N(3))(2)](n)() in which L = 4-cyanopyridine (1) or 3-acetylpyridine (2) have been obtained and structurally and magnetically characterized. Both compounds crystallize in the monoclinic system, space group P2(1)/a, formula [C(12)H(8)MnN(10)] with a = 13.286(4) Å, b = 8.340(3) Å, c = 13.579(4) Å, beta = 90.55(2) degrees, and Z = 4 for compound 1 and space group P2(1)/c, formula [C(14)H(14)MnN(8)O(2)] with a = 11.843(4) Å, b = 9.550(3) Å, c = 14.998(5) Å, beta = 105.99(3) degrees, and Z = 4 for compound 2. The two compounds show a similar arrangement of alternating end-to-end and end-on azido bridges between the manganese atoms, giving magnetically alternated ferro-antiferromagnetic two-dimensional compounds. The pyridyl ligands coordinated to the axial sites stick out above and below the 2-D sheets, and intersheet pi-pi interactions are formed between the pyridyl ligands, playing a role in the structural differences. The low-temperature magnetic properties of 1 and 2, together with those of the previously reported compounds with L = pyridine (3), 4-acetylpyridine (4), and ethyl isonicotinate (5), are reported. Magnetic ordering and spontaneous magnetization is achieved at T(C) = 18, 16, 40, 28, and 16 K for 1-5, respectively.

Journal Article↗
PubMed2001

Long-range magnetic order in Mn[N(CN)2]2(pyz) (pyz = pyrazine). Susceptibility, magnetization, specific heat, and neutron diffraction measurements and electronic structure calculations.

Using dc magnetization, ac susceptibility, specific heat, and neutron diffraction, we have studied the magnetic properties of Mn[N(CN)2]2(pyz) (pyz = pyrazine) in detail. The material crystallizes in the monoclinic space group P2(1)/n with a = 7.3248(2), b = 16.7369(4), and c = 8.7905 (2) A, beta = 89.596 (2) degrees, V = 1077.65(7) A(3), and Z = 4, as determined by Rietveld refinement of neutron powder diffraction data at 1.35 K. The 5 K neutron powder diffraction data reflect very little variation in the crystal structure. Interpenetrating ReO3-like networks are formed from axially elongated Mn(2+) octahedra and edges made up of mu-bonded [N(CN)2](-) anions and neutral pyz ligands. A three-dimensional antiferromagnetic ordering occurs below T(N) = 2.53(2) K. The magnetic unit cell is double the nuclear one along the a- and c-axes, giving the (1/2, 0, 1/2) superstructure. The crystallographic and antiferromagnetic structures are commensurate and consist of collinear Mn(2+) moments, each with a magnitude of 4.15(6) mu(B) aligned parallel to the a-direction (Mn-pyz-Mn chains). Electronic structure calculations indicate that the exchange interaction is much stronger along the Mn-pyz-Mn chain axis than along the Mn-NCNCN-Mn axes by a factor of approximately 40, giving rise to a predominantly one-dimensional magnetic system. Thus, the variable-temperature magnetic susceptibility data are well described by a Heisenberg antiferromagnetic chain model, giving g = 2.01(1) and J/k(B) = -0.27(1) K. Owing to single-ion anisotropy of the Mn(2+) ion, field-induced phenomena ascribed to spin-flop and paramagnetic transitions are observed at 0.43 and 2.83 T, respectively.

Journal Article↗
PubMed2002

Quantum tunneling of magnetization in a new [Mn18]2+ single-molecule magnet with s = 13.

The reaction between 2-(hydroxyethyl)pyridine (hepH) and a 2:1 molar mixture of [Mn3O(O2CMe)6(py)3](ClO4) and [Mn3O(O2CMe)6(py)3](py) in MeCN leads to isolation of [Mn18O14(O2CMe)18(hep)4(hepH)2(H2O)2](ClO4)2 (1) in 10% yield. The complex is 2MnII,16MnIII and consists of a Mn4O6 central unit to either side of which is attached a Mn7O9 unit. Magnetization data collected in the 2.0-4.0 K and 20-50 kG ranges were fit to yield S = 13, g = 1.86, and D = -0.13 cm-1 = -0.19 K, where D is the axial zero-field splitting parameter. AC susceptibility studies in the 0.04-4.0 K range at frequencies up to 996 Hz display out-of-phase (chiM' ') signals, indicative of a single-molecule magnet (SMM). Magnetization vs applied DC field scans exhibit hysteresis at <1.0 K, confirming 1 to be a SMM. DC magnetization decay data were collected on both a microcrystalline sample and a single crystal, and the combined data were used to construct an Arrhenius plot. Between 3.50 and 0.50 K, the relaxation rate is temperature-dependent with an effective barrier to relaxation (Ueff) of 14.8 cm-1 = 21.3 K. Below ca. 0.25 K, the relaxation rate is temperature-independent at 1.3 x 10-8 s-1, indicative of quantum tunneling of magnetization (QTM) between the lowest energy Ms = +/-13 levels of the S = 13 state. Complex 1 is both the largest spin and highest nuclearity SMM to exhibit QTM.

Journal Article↗
PubMed2003

Mechanism of a strongly anisotropic MoIII-CN-MnII spin-spin coupling in molecular magnets based on the [Mo(CN)(7)](4-) heptacyanometalate: a new strategy for single-molecule magnets with high blocking temperatures.

Unusual spin coupling between Mo(III) and Mn(II) cyano-bridged ions in bimetallic molecular magnets based on the [Mo(III)(CN)(7)](4-) heptacyanometalate is analyzed in terms of the superexchange theory. Due to the orbital degeneracy and strong spin-orbit coupling on Mo(III), the ground state of the pentagonal-bipyramidal [Mo(III)(CN)(7)](4-) complex corresponds to an anisotropic Kramers doublet. Using a specially adapted kinetic exchange model we have shown that the Mo(III)-CN-Mn(II) superexchange interaction is extremely anisotropic: it is described by an Ising-like spin Hamiltonian JS(z)(Mo) S(z)(Mn) for the apical pairs and by the J(z)S(z)(Mo) S(z)(Mn) + J(xy)(Sx(Mo) Sx(Mn) + Sy(Mo) Sy(Mn)) spin Hamiltonian for the equatorial pairs (in the latter case J(z) and J(xy) can have opposite signs). This anisotropy resulted from an interplay of several Ising-like (Sz(Mo) Sz(Mn)) and isotropic (S(Mo)S(Mn)) ferro- and antiferromagnetic contributions originating from metal-to-metal electron transfers through the pi and sigma orbitals of the cyano bridges. The Mo(III)-CN-Mn(II) exchange anisotropy is distinct from the anisotropy of the g-tensor of [Mo(III)(CN)(7)](4-); moreover, there is no correlation between the exchange anisotropy and g-tensor anisotropy. We indicate that highly anisotropic spin-spin couplings (such as the Ising-like JS(z)(Mo) S(z)(Mn)) combined with large exchange parameters represent a very important source of the global magnetic anisotropy of polyatomic molecular magnetic clusters. Since the total spin of such clusters is no longer a good quantum number, the spin spectrum pattern can differ considerably from the conventional scheme described by the zero-field splitting of the isotropic spin of the ground state. As a result, the spin reorientation barrier of the magnetic cluster may be considerably larger. This finding opens a new way in the strategy of designing single-molecule magnets (SMM) with unusually high blocking temperatures. The use of orbitally degenerate complexes with a strong spin-orbit coupling (such as [Mo(III)(CN)(7)](4-) or its 5d analogues) as building blocks is therefore very promising for these purposes.

Journal Article↗
PubMed2004

Single-molecule magnets of ferrous cubes: structurally controlled magnetic anisotropy.

Tetranuclear Fe(II) cubic complexes were synthesized with Schiff base ligands bridging the Fe(II) centers. X-ray structural analyses of six ferrous cubes, [Fe4(sap)4(MeOH)4].2H2O (1), [Fe4(5-Br-sap)4(MeOH)4] (2), [Fe4(3-MeO-sap)4(MeOH)4].2MeOH (3), [Fe4(sae)4(MeOH)4] (4), [Fe4(5-Br-sae)4(MeOH)4].MeOH (5), and [Fe4(3,5-Cl2-sae)4(MeOH)4] (6) (R-sap and R-sae were prepared by condensation of salicylaldehyde derivatives with aminopropyl alcohol and aminoethyl alcohol, respectively) were performed, and their magnetic properties were studied. In 1-6, the alkoxo groups of the Schiff base ligands bridge four Fe(II) ions in a mu3-mode forming [Fe4O4] cubic cores. The Fe(II) ions in the cubes have tetragonally elongated octahedral coordination geometries, and the equatorial coordination bond lengths in 4-6 are shorter than those in 1-3. Dc magnetic susceptibility measurements for 1-6 revealed that intramolecular ferromagnetic interactions are operative to lead an S = 8 spin ground state. Analyses of the magnetization data at 1.8 K gave the axial zero-field splitting parameters (D) of +0.81, +0.80, +1.15, -0.64, -0.66, and -0.67 cm(-1) for 1-6, respectively. Ac magnetic susceptibility measurements for 4-6 showed both frequency dependent in- and out-of-phase signals, while 1-3 did not show out-of-phase signals down to 1.8 K, meaning 4-6 are single-molecule magnets (SMMs). The energy barriers to flip the spin between up- and down-spin were estimated to 28.4, 30.5, and 26.2 K, respectively, for 4-6. The bridging ligands R-sap2- in 1-3 and R-sae2- in 4-6 form six- and five-membered chelate rings, respectively, which cause different steric strain and Jahn-Teller distortions at Fe(II) centers. The sign of the D value was discussed by using angular overlap model (AOM) calculations for irons with different coordination geometry.

Journal Article↗
PubMed2005

Alignment of carbon nanotubes under low magnetic fields through attachment of magnetic nanoparticles.

The alignment of multiwalled carbon nanotubes (MWNTs) has been accomplished through deposition of uniform layers of magnetite/maghemite nanoparticles (diameter = 6-10 nm) and use of an external magnetic field. The coating of CNTs with magnetic nanoparticles was performed by combining the polymer wrapping and layer-by-layer (LbL) assembly techniques. The particle-coated MWNTs are superparamagnetic and can be aligned at room temperature on any substrate by deposition from an aqueous solution in an external field B = 0.2 T. The volume magnetization of the particle coated MWNTs is found to be enhanced by 17% compared to the pure particles in a powder indicating that either the adsorption process onto the CNTs changes the particle magnetization, or the MWNTs carry an intrinsic magnetization due to remaining Ni used as a catalyst for the growth process.

Letter↗
PubMed2006

Quasi-one-dimensional molecular magnets based on derivatives of (fluorobenzyl)pyridinium with the [M(mnt)2] monoanion (M = Ni, Pd or Pt; mnt2- = maleonitriledithiolate): syntheses, crystal structures and magnetic properties.

The syntheses, structural characterizations and magnetic behaviors of three new complexes, 1-(3',4',5'-trifluorobenzyl)pyridinium [M(mnt)2]- [M = Ni (1), Pd (2) or Pt (3)], are reported. These complexes are isomorphous and their prominent structural character is that the [M(mnt)2]- anions form columnar stacks, in which the dimerization was observed. Complexes 2 and 3 are diamagnetic, while 1 possesses an energy gap of 2474 K. For crystal 4, 1-(4'-fluorobenzyl)pyridinium [Ni(mnt)2] (its structure and magnetic susceptibility were briefly reported earlier), the magnetic behavior can be divided into two regimes, namely, weakly ferromagnetic coupling above 93 K and strongly antiferromagnetic coupling below 93 K. A transition occurs at 93 K which switches the magnetic exchange nature from ferromagnetic to antiferromagnetic. A sharp thermal abnormality with lambda-shape, associated with the transition, appears from its heat capacity measurement to indicate that the transition is first order. The temperature dependences of the superlattice diffractions revealed the existence of the pretransitional phenomena up to at least 140 K. The unusual magnetic behavior of 4, such as the origin of the ferromagnetic interaction in the high temperature phase and what causes the spin transition, are discussed further.

Journal Article↗
PubMed2006

A robust microporous 3D cobalt(II) coordination polymer with new magnetically frustrated 2D lattices: single-crystal transformation and guest modulation of cooperative magnetic properties.

A microporous 3D cobalt(II) coordination polymer featuring pillared layers [Co(2)(ma)(ina)](n) x 2nH(2)O (1 x 2H(2)O) (ma = malate, ina = isonicotinate) was generated by hydrothermal treatment with a void volume of 25.8%, in which the in-situ generated ma ligands connect the Co(II) ions into a 2D lattice with mixed and multiple exchange-bridges, affording a new geometrical topology different from the Kagomé lattice and leading to spin frustration. The rigid ina-pillared metallic-layered structure could retain 3D structural ordering upon guest removal and exchange. By soaking guest-free host in MeOH and methanamide (HCONH(2)) solutions, single crystals of dehydrated were transformed into single crystals of 1 x MeOH and 1 x HCONH(2), respectively, without apparent host-structural changes. 1 can also be rehydrated into 1 x 2H(2)O'. The guest-inclusion crystals have been characterized by X-ray single-crystal diffraction at 293 K and 93 K, confirming the single-crystal-to-single-crystal transformations and providing detailed information of the guest molecules confined in the subnanospace and host-guest and/or guest-guest hydrogen-bonding interactions. The magnetic behaviours of this family of porous magnetic materials are complex due to the influences of multiple metal sites, intra- and inter-layer exchanges, spin-orbit coupling, as well as geometrical frustration, which show magnetic ordering at <2 K, 3.5 K, 3.5 K, and 8 K for 1, 1 x MeOH, 1 x HCONH(2), and 1 x 2H(2)O, respectively, due to the different size of guest molecules along with the different host-guest interaction, which may slightly modify the path of magnetic exchange, decrease the intensity of the spin-frustration in the 2D lattice, and cooperatively enhance the magnetic ordering temperature.

Journal Article↗
PubMedDate not supplied

Magnetic flow sorting using a model system of human lymphocytes and a colloidal magnetic label.

Cells of identical physical properties that differ in the expression of surface proteins can be sorted conveniently using immunospecific stains conjugated to fluorescent, or magnetic, labels. Immunomagnetic cell sorting using commercial batch sorters offers advantages of high sorting capacity, high viability of sorted fractions, and high depletion rates; its disadvantages are low enrichment rate and batch processing. The authors developed and tested a continuous, flow-through magnetic cell sorter for small volume, experimental cell enrichment. Freshly isolated human peripheral lymphocytes were labeled using an immunofluoromagnetic sandwich consisting of mouse anti human CD8 monoclonal antibody-fluorescein conjugate and rat anti mouse polyclonal antibody-colloidal iron-dextran conjugate. A total of 2-3 min lymphocytes were sorted per hour using a saturation magnetic field of 1.334 T and a five channel sorter. The fluorescent cells were distributed among the channels in relation to their fluorescence intensity and magnetic susceptibility. The purity (68-85%) and enrichment rates (16-34x) were comparable to those of commercial batch magnetic separators; sorting capacity and recovery of the enriched fractions (up to 32%) were limited by the small scale of the sorter. Future direction is focused on increasing the resolution, recovery, and sorting capacity of the enriched fractions, and testing the sorter on other cell systems.

Animals↗
PubMed2001

Evolution of induced axial magnetization in a two-component magnetized plasma.

In this paper, the evolution of the induced axial magnetization due to the propagation of an electromagnetic (em) wave along the static background magnetic field in a two-component plasma has been investigated using the Block equation. The evolution process induces a strong magnetic anisotropy in the plasma medium, depending nonlinearly on the incident wave amplitude. This induced magnetic anisotropy can modify the dispersion relation of the incident em wave, which has been obtained in this paper. In the low frequency Alfven wave limit, this dispersion relation shows that the resulting phase velocity of the incident wave depends on the square of the incident wave amplitude and on the static background magnetic field of plasma. The analytical results are in well agreement with the numerically estimated values in solar corona and sunspots.

Journal Article↗
PubMed2002

Binding of biological effectors on magnetic nanoparticles measured by a magnetically induced transient birefringence experiment.

We have investigated the relaxation of the magnetically induced birefringence in a suspension of magnetic nanoparticles in order to detect the binding reaction of polyclonal antibodies on the particle surface. The birefringence relaxation is driven by the rotational diffusion of the complex formed by the magnetic nanoparticles bound to the antibody and thus is directly related to the hydrodynamic size of this complex. Birefringence relaxations are well described by stretched exponential laws revealing a polydisperse distribution of hydrodynamic diameters. Comparing the size distribution of samples with different initial ratios of immunoglobuline added per magnetic nanoparticles, we evidence the graft of an antibody on particle and eventually the onset of particles aggregation. Measurements on samples separated in size by gel filtration demonstrate the robustness of our experiment for the determination of size distribution and its modification due to the adsorption of a macromolecule. The immunoglobuline binding assay is performed comparatively for ionic magnetic nanoparticles with different coatings.

Journal Article↗
PubMed2003

Shear- and magnetic-field-induced ordering in magnetic nanoparticle dispersion from small-angle neutron scattering.

Small-angle neutron scattering experiments have been performed to investigate orientational ordering of a dispersion of rod-shaped ferromagnetic nanoparticles under the influence of shear flow and static magnetic field. In this experiment, the flow and flow gradient directions are perpendicular to the direction of the applied magnetic field. The scattering intensity is isotropic in zero-shear-rate or zero-applied-field conditions, indicating that the particles are randomly oriented. Anisotropic scattering is observed both in a shear flow and in a static magnetic field, showing that both flow and field induce orientational order in the dispersion. The anisotropy increases with the increase of field and with the increase of shear rate. Three states of order have been observed with the application of both shear flow and magnetic field. At low shear rates, the particles are aligned in the field direction. When increasing shear rate is applied, the particles revert to random orientations at a characteristic shear rate that depends on the strength of the applied magnetic field. Above the characteristic shear rate, the particles align along the flow direction. The experimental results agree qualitatively with the predictions of a mean field model.

Journal Article↗
PubMed2004

Dynamics of a flexible magnetic chain in a rotating magnetic field.

The model of an elastic magnetic rod is applied for a study of a behavior of the flexible magnetic particle chain in a rotating magnetic field. By numerical simulation it is shown that behavior of a flexible magnetic chain is characterized by the existence of a critical frequency beyond which the dynamics of the rod is periodic with subsequent stages of bending and straightening. The value of the critical frequency found is explained by a simple model. Below the critical frequency the chain is bent and rotates synchronously with a field. It is illustrated that in particular cases the considered model reproduces phenomena observed experimentally and numerically for the magnetic particle chains in magnetorheological suspensions. It is emphasized that the present approach gives the general framework for the description of different phenomena in magnetorheological suspensions.

Journal Article↗