Effect of magnetic field intensity and γ-Fe2O3 nanoparticle additive on electrical conductivity and viscosity of magnetorheological carbonyl iron suspension-based membranes

Smart membranes based on an absorbent cloth microfiber material and silicone oil were prepared using a fixed volume concentration of carbonyl iron and various volume concentrations of gamma-Fe2O3 additive nanoparticles. The membranes were then used to manufacture magnetoresistors, whose resistance was measured under an applied magnetic field with a magnetic flux density up to 250 mT. The electrical conductivity and viscosity of the membranes increased with increasing magnetic field intensity, while at a fixed magnetic field strength, the electrical conductivity and viscosity decreased with increasing gamma-Fe2O3 concentration. A theoretical model to explain these results was developed further in the framework of a dipolar approximation.