Coir dust reinforced polymer composites are prepared with epoxy resin as the matrix. The dielectric parameters (relative permittivity ε′, dielectric loss ε′′), AC conductivity σ, and resistivity ρ of pure epoxy resin and composites with different weight percent of coir dust were obtained in a frequency range of 100 Hz to 1 MHz, and temperature range of 30—150°C. The experimental results show that ε′, ε′′, and σ are increased and ρ is decreased with the addition of coir dust in epoxy resin. It is also observed that the dielectrical properties of the composites showed a strong dependence on frequency and temperature. The ε′ and ε′′ increases with increasing temperature because of greater movement of the dipole molecular chains and decreases with increasing frequency due to the orientation polarization. The conductivity of the composite is increased, and the resistivity of composite is decreased with increasing frequency.
We have fabricated Fe3O4/p-Si heterojunction using pulsed laser deposition technique and explored its electro-magnetic transport properties. The heterojunction exhibits backward rectifying property at all temperatures, and appraisal of giant junction magnetoresistance (JMR) is observed at room temperature (RT). Conspicuously, the variation and sign change of JMR as a function of electric field is observed at RT. The backward rectifying behavior of the device is ascribed to the highly doped p-type (p++) semiconducting nature of Fe3O4, and the origin of electric field (voltage) dependence of magnetoresistance is explained proposing electronic band diagram of Fe3O4/SiO2/p-Si heterojunction. This interesting result may have importance to integrate Si-based magnetoresistance sources in multifunctional spintronic devices.
The polycrystalline CoFe2O4 (CFO) film on cantilever substrate of silicon was grown using pulsed laser deposition (PLD) method and investigated its in-plane and out-of-plane magnetostrictive strain at room temperature (300 K) using the indigenous optical Cantilever Beam Magnetometer (CBM). The film shows a high compressive magnetostrictive strain of ‒ 387 ppm and ‒ 708 ppm for in-plane and out-of-plane configurations, respectively. Considerably, the magnetostrictive strain loops (λ‒H) possess a certain degree of hysteresis with a symmetric butterfly shape. The origin of large compressive magnetostriction of CFO film is attributed to the non-180° domain wall motion followed by 90° domain rotation. The large values of saturation magnetostrictive strain make CFO film a suitable candidate in sensor design for different purposes.
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