Magnetoresistive Properties of Nanocomposites Based on Ferrite Nanoparticles and Polythiophene

Abstract

In the presented study, we have synthesized six nanocomposites based on various magnetic nanoparticles and a conducting polymer, poly(3-hexylthiophene-2,5-diyl) (P3HT). Nanoparticles were either coated with squalene and dodecanoic acid or with P3HT. The cores of the nanoparticles were made of one of three different ferrites: nickel ferrite, cobalt ferrite, or magnetite. All synthesized nanoparticles had average diameters below 10 nm, with magnetic saturation at 300 K varying between 20 to 80 emu/g, depending on the used material. Different magnetic fillers allowed for exploring their impact on the conducting properties of the materials, and most importantly, allowed for studying the influence of the shell on the final electromagnetic properties of the nanocomposite. The conduction mechanism was well defined with the help of the variable range hopping model, and a possible mechanism of electrical conduction was proposed. Finally, the observed negative magnetoresistance of up to 5.5% at 180 K, and up to 1.6% at room temperature, was measured and discussed. Thoroughly described results show the role of the interface in the complex materials, as well as clarify room for improvement of the well-known magnetoelectric materials.

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“…These effects can be exacerbated by the thermal annealing, which is usually performed in vacuum or inert atmosphere. Therefore, additional Fe 3 O 4 functionalization with organic molecules as acetic acid, amine, polyvinyl acetate [24,26,[38][39][40], or inorganic coatings as SiO 2 or ZrO 2 [29,[41][42][43] were studied in order to enhance the room-temperature magnetoresistance, by improving the NPs arrays and/or protecting the nanoparticle surface from oxidation. However, this step complicates the fabrication process and it is found that the enhancement of TMR is still far away from the predicted value.…”

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