Evolution of the magnetization response of magneto-active elastomers made with hard-magnetic M-type barium hexaferrite particles

Abstract

ABSTRACTMagneto active elastomers (MAE), particulate filled magneto-sensitive composites, were made with increasing volume contents of 325 mesh M-type barium hexaferrite (BAM) particles within a silicone elastomer matrix. The volume contents of BAM ranged from 10% to 35% v/v. Vibrating sample magnetometery measurements showed that the remanence and saturation, both per unit magnetic material, increased by 50% from 10%v/v to 20%v/v before slowing decreasing as v/v increased to 35%. The results clearly show in peak in the effectiveness of the embedded particles to produce bulk magnetization near 20% v/v. One possible means for the increase stems from alignment of the magnetization of the particles and hence of the magnetic domains within particles. To assess this possible alignment, Gaussian probability distribution of magnetization orientations was fit to the experimental data to ascertain the change in the distribution as a function of v/v. Results showed 20% v/v had the highest degree of alignment. The results highlight, at a bulk scale, the possible evolution of microstructure within the composite. Similar results have been seen in image analysis of physical particle distribution of other magneto-sensitive particulate composites. The results suggest that effective processing techniques can be used to greatly enhance the bulk magnetization of these and similar composites, paving the way for decreasing required magnetic content to achieve target response specification and possibly resulting miniaturization.