Critical bending and magnetic shape memory effect in magnetoactive elastomers

TL;DR

This study investigates the critical bending behavior and magnetic shape memory effect in magnetoactive elastomers, revealing a critical point where mechanical stability is lost and magnetic symmetry is reduced, with hysteresis and temperature effects influencing the response.

Contribution

First demonstration of critical bending and magnetic shape memory effects in magnetoactive elastomers with detailed analysis of critical phenomena and temperature influences.

Findings

Critical bending occurs with a critical exponent and singular derivative.

Magnetic symmetry reduction and torque emergence at the critical point.

Hysteresis in magnetic field dependence linked to magneto-rheological effects.

Abstract

The results of a study of magnetoactive elastomers (MAEs) consisting of an elastomer matrix with embedded ferromagnetic particles are presented. A continuous critical bending induced by the magnetic field, characterized by a critical exponent for the bending magnitude, and the derivative of which has a singularity in the critical region is reported for the first time. The mechanical stability loss and the symmetry reduction of the magnetic state, which are interrelated with each other, take place at the critical point. The magnetization in the high-symmetric state (below the critical point) is directed along the magnetic field and the torque is absent. Above the critical point, the magnetization and the magnetic field are noncollinear and there arises a torque, which is self-consistent with the bending. The magnetic field dependence of the MAE bending was found to have a hysteresis, which is associated with the magneto-rheological effect. The shape memory effect was also obtained for the MAE bending in a cycle consisting of magnetization, cooling (at H=/0), and heating (at H=0). The influence of the critical glass transition temperature of the matrix, as well as its melting/solidification temperature, on the magnetic shape memory effect was studied.