Microwave Shielding Characteristics of ${\hbox {PMMA/BiFeO}}_{3}$ Composites

BiFe_1-xSm_xO₃ composites with different samarium (Sm) concentration (x=5-20%) in BFO₃ were fabricated by the solid-state method. Their structure and magnetic property due to the samarium substitution in BFO₃ were analyzed by the X-ray diffractometer and vibration sample magnetometer responses, respectively. The complex permeability (μ = μ\´-jμ") and shielding effectiveness (SE) of powder-resin composites consisting of magnetic particles (BiFe_1-xSm_xO₃) embedded into a dielectric matrix (PMMA) were studied at the microwave frequencies. The samarium concentration dependence of permeability and SE was measured using the free-space method. We found that the magnetic properties of the Sm-substitute BFO₃ mainly lead to the shielding effect for the PMMA/BiFe_1-xSm_xO₃ composites. In this paper, we demonstrate the gradual change of the shielding effect and permeability of the PMMA/BiFe_1-xSm_xO₃ composites in the microwave range.