| Summary: | We present a simple, low-cost, and environmental-friendly method for the fabrication of hybrid magnetorheological composites (hMCs) based on cotton fibers soaked with a mixture of silicone oil (SO), carbonyl iron (CI) microparticles, and iron oxide microfibers (<inline-formula><math display="inline"><semantics><mi>μ</mi></semantics></math></inline-formula>F). The obtained hMCs, with various ratios (<inline-formula><math display="inline"><semantics><mo>Φ</mo></semantics></math></inline-formula>) of SO and <inline-formula><math display="inline"><semantics><mi>μ</mi></semantics></math></inline-formula>F, are used as dielectric materials for manufacturing electrical devices. The equivalent electrical capacitance and resistance are investigated in the presence of an external magnetic field, with flux density <i>B</i>. Based on the recorded data, we obtain the variation of the relative dielectric constant (<inline-formula><math display="inline"><semantics><mrow><msub><mi>ϵ</mi><mi mathvariant="normal">r</mi></msub><msup><mrow></mrow><mo>′</mo></msup></mrow></semantics></math></inline-formula>), and electrical conductivity (<inline-formula><math display="inline"><semantics><mi>σ</mi></semantics></math></inline-formula>), with <inline-formula><math display="inline"><semantics><mo>Φ</mo></semantics></math></inline-formula>, and <i>B</i>. We show that, by increasing <inline-formula><math display="inline"><semantics><mo>Φ</mo></semantics></math></inline-formula>, the distance between CI magnetic dipoles increases, and this leads to significant changes in the behaviour of <inline-formula><math display="inline"><semantics><mrow><msub><mi>ϵ</mi><mi mathvariant="normal">r</mi></msub><msup><mrow></mrow><mo>′</mo></msup></mrow></semantics></math></inline-formula> and <inline-formula><math display="inline"><semantics><mi>σ</mi></semantics></math></inline-formula> in a magnetic field. The results are explained by developing a theoretical model that is based on the dipolar approximation. They indicate that the obtained hMCs can be used in the fabrication of magneto-active fibers for fabrication of electric/magnetic field sensors and transducers.
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