Magnetostriction in ferrogels based on physical and chemical networking with embedded strontium hexaferrite particles

A P Safronov,E A Mikhnevich

doi:10.1088/1742-6596/1389/1/012057

Abstract

Magnetostriction of ferrogels based on physical and chemical networking with embedded strontium hexaferrite particles was studied in 420 mT uniform magnetic field. Ferrogel with physical networking was based on natural polysaccharide – guar gum, which gelates due to formation of H-bonds. Ferrogel with chemical networking was synthesized by radical polymerization of acrylamide. Magnetostriction of the physical ferrogel resulted in the increase of length of the gel specimen along the field lines and in the proportional decrease of its width in the direction across the field lines. In case of chemical ferrogel, both the length and the width increased in the uniform magnetic field leading to the increase of the ferrogel volume.

Highlights

Magnetostriction is a phenomenon when ferromagnetic materials change their shape or/and dimensions during magnetization in applied magnetic field
A spherical sample FGI with approximate diameter of 3 mm was pinned by a needle mounted vertically downside at the cap of the optical cuvette Several droplets of water were put in the cuvette to provide saturated water vapor inside and to prevent weight loss of the ferrogel due to evaporation
As the physical gels are typically very soft, the spherical sample has acquired the shape close to ellipsoid in the gravity field, see figure 4 (a), where the minor and major semi-axes of ellipsoid are marked as a and b, respectively

Summary

Introduction

Magnetostriction is a phenomenon when ferromagnetic materials change their shape or/and dimensions during magnetization in applied magnetic field. The elongation of a magnetic composite along the field lines (positive magnetostriction) was experimentally confirmed in several reports [4,5,6,7]. It is important, to point out that the mentioned theoretical result refers to magnetostriction of i) noncompressible ii) uniformly magnetized composite. To point out that the mentioned theoretical result refers to magnetostriction of i) noncompressible ii) uniformly magnetized composite If one of these two conditions fails, there

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Conclusion