A kinetic model for magnetostriction of a ferrogel with physical networking

Kinetics of magnetostriction of ferrogel with physical networking based on natural polysaccharide guar gum with embedded strontium hexaferrite magnetic particles were studied in the uniform magnetic field 420 mT. An ellipsoidal sample was elongated by 37% along the applied field and contracted by 15% in the transverse direction, while its volume was kept constant. The characteristic time of magnetostriction was 440 s. Dynamic mechanical analysis in an oscillatory mode showed that the deformation of ferrogel is mostly elastic rather than viscous. Its storage modulus was almost constant in a frequency range of 0.1-100 Hz and by at least an order of magnitude larger than the loss modulus. Meanwhile, a developed theoretical model based on the elasto-viscous behaviour of the ferrogel failed to estimate correctly the experimental value of its magnetostriction. Calculated values of the elongation of ferrogel in the field were several orders of magnitude lower than those observed in the experiment for the ferrogel with physical networking. Consistency between the experiment and the theory was achieved using the alternative consideration based on the deformation of a liquid droplet of ferrofluid. The applicability of such an approach was discussed concerning structural relaxation properties of the ferrogel with physical networking. This article is part of the theme issue 'Transport phenomena in complex systems (part 1)'.