Electromagnetomechanical coupling characteristics of plastoferrites

Abstract

The impetus of this work was to investigate the electromagnetic and tensile properties of several commercially available plastoferrites (PFs) at ambient conditions. The approach involved selection of a set of PFs and measuring their complex effective permittivity ε=ε′−jε″ and permeability μ=μ′−jμ″ under uniaxial stress at microwave frequencies (0.1–4.5GHz) and room temperature. We analyze the ε and μ spectra for tensilely strained PFs up to 3%. Comparing our experimental ε data against several dielectric relaxational behaviors, we find that the main physics cannot be understood with a single relaxation mechanism. We then go on to consider the magnetic permeability spectra in the microwave range of frequencies and show that an appropriate magnetization mechanism is given by the gyromagnetic spin resonance mechanism. We use a combination of Bruggeman mean field analysis and Landau-Lifshitz-Gilbert modeling to reproduce the experimental bimodal line-shape characteristics of the effective complex magnetic permeability. These findings are discussed in light of the polydispersity in size of the ferrite gains contained in the PFs. The vibrating sample magnetometry investigations of the static magnetization are found to be consistent with this modeling. In addition, the analysis shows also how magnetized PFs respond to electromagnetic waves, and we evaluate the hysteretic behaviors of ε and μ. More importantly we show that the ε and μ measurements under stress can be explained in terms of a Gaussian molecular network model in the limit of low stress. The present results have important applications in magnetoactive smart composite materials, e.g., flexible circuit technology in the electronics industry (sensors, actuators, and micromechanical systems), functionalized artificial skin, and muscles for robotic applications.