Temperature-dependent magnetic properties of a magnetoactive elastomer: Immobilization of the soft-magnetic filler

Abstract

Magnetic properties of a magnetoactive elastomer (MAE) filled with µm-sized soft-magnetic iron particles have been experimentally studied in the temperature range between 150 K and 310 K. By changing the temperature, the elastic modulus of the elastomer matrix was modified and it was possible to obtain magnetization curves for an invariable arrangement of particles in the sample as well as in the case when the particles were able to change their position within the MAE under the influence of magnetic forces. At low (less than 220 K) temperatures, when the matrix becomes rigid, the magnetization of the MAE does not show a hysteresis behavior and it is characterized by a negative value of the Rayleigh constant. At room temperature, when the polymer matrix is compliant, a magnetic hysteresis exists and exhibits local maxima of the field dependence of the differential magnetic susceptibility. The appearance of these maxima is explained by the elastic resistance of the matrix to the displacement of particles under the action of magnetic forces.

Theoretical method for calculation of effective properties of composite materials with reconfigurable microstructure: Electric and magnetic phenomena

“…Here we use the dependence of the magnetic permeability of inclusions in the form (12). The value of the two parameters that determine the numerical values are taken from the paper [64]: Figure 3 shows the field and concentration dependences of the magnetic permeability of MAE obtained from the solution of the system of equations (11)(12) and a comparison with the experiment of [11]. It is seen that there is an excellent agreement between theory and experiment for a conventional set of parameters.…”

“…    c , с c p p  H . This is the qualitative explanation of the magnetodielectric effect, because the dielectric 11 properties will depend on the external magnetic field as well. Figure 2 Figure 2 (b) shows that the variation of the lossless dielectric constant increases with decreasing critical field Hc.…”

“…Let us consider the method of calculating the concentration dependence of the effective magnetic permeability in the absence of RS. This is the case in conventional polymer-based ferromagnetic composite materials [52][53][54] or in MAEs at low temperatures [11]. To be specific, consider a MAE specimen with rigidized PDMS polymer matrix at low temperatures (below 220 K) [11].…”

“…RS can also happen during measurement. In the following, we will use as a striking example magnetoactive elastomers (MAEs) at room temperature [10,11]. For instance, when measuring the effective magnetic permeability of a MAE with a soft polymer matrix, it is necessary to put a MAE specimen into a magnetic field.…”

“…Any physical property related to the arrangement of inclusions within the composite material will change [16]. If the matrix is soft (Young's modulus is smaller than approximately 30 kPa), the RS of the particulate filler can be significant even at moderate (100 -300 mT) magnetic flux densities [7,11,[17][18][19][20][21].…”