Negative and Reversible Magnetorheological Response for Magnetic Rubbers

A material exhibiting a reversible decrease in elastic modulus upon application of a magnetic field has been successfully developed for the first time. The material is a composite of natural rubber and carbonyl iron with a particle diameter of 8.3 μm. The storage modulus in the absence of magnetic field is 155 kPa and it decreases to 89.5 kPa by applying a magnetic field of 500 mT. The rubber composite underwent reversible changes in the dynamic modulus even after 30 cycles of on-off switching of the magnetic field.