Magnetorheological elastomers are a type of smart hybrid material where elastic properties of a soft elastomer matrix are combined with magnetic properties of magnetic micro particles. This combination leads to a complex interplay of magnetic and elastic phenomena, of which the magnetorheological effect is the best described. In this paper, magnetically hard NdFeB-particles were used to obtain remanent magnetic properties. X-ray microtomography has been utilised to analyse the particle movement induced by magnetic fields. A particle tracking was performed; thus, it was possible to characterise the movement of individual particles. Beyond that, a comprehensive analysis of the orientation of all particles was performed at different states of magnetisation and global particle arrangements. For the first time, this method was successfully applied to a magnetorheological material with a technically relevant amount of magnetic NdFeB-particles. A significant impact of the magnetic field on the rotation and translation of the particles was shown.

The first magnetization loop and the first stress–strain cycle of magnetoactive elastomers (MAEs) in a magnetic field differ considerably from the following loops and cycles, possibly due to the internal restructuring of the magnetic filler particles and the matrix polymer chains. In the present study, the irreversible magnetization processes during the first magnetization of MAEs with different filler compositions and tensile moduli of the matrix are studied by first-order reversal curve (FORC) measurements. For MAEs with mixed magnetic NdFeB/Fe fillers the FORC distributions and magnetization distributions of the first major loop reveal a complex irreversible magnetization behavior at interaction fields H_u < −50 kA m⁻¹ due to the magnetostatic coupling between the magnetically hard NdFeB and the magnetically soft Fe particles. This coupling is enhanced either if the interparticle distance is reduced by particle motion and restructuring or by an increase in the particle densities. If the stiffness of the matrix is increased, the structuring and thus the interparticle interactions are suppressed and the magnetization reversal is dominated by domain processes in the NdFeB particles at high coercive fields of H_c > 600 kA m⁻¹.