Flexible organic semiconductor switching enabled by the magnetoresistance effect

Abstract

Recent advancements in material sciences have placed significant emphasis on the development of materials with smart properties and functionalities, that can be controlled or adjusted by external stimuli. We present a study of polydimethylsiloxane/polypyrrole/Ni nanoparticle composites as testbeds for Organic Magnetoresistance (OMAR) application. The magnetoresistance sensitivity, (ΔR/R₀), of flexible organic composites at room temperature typically falls below one, for millitesla-scale magnetic fields. Our experiments demonstrate that the fabricated films exhibit a notable magnetoresistance effect, with relative electrical resistance changes of 5.2, under a weak magnetic field of 10⁻² T under ambient conditions. We show that these composite films are flexible, conductive, and exhibit heighted OMAR capabilities, with switching rates stable up to 5 kHz. The magnetic permeability of the samples is investigated using a bespoke time-domain magnetic spectrometer, revealing enhanced diamagnetic behavior. This underpins the magnetic resistance of the composite, because of spin injection and consequent interaction with the magnetic field. This study introduces the first example of a single flexible film structure capable of detecting weak magnetic fields, as low as 10⁻² T at room temperature, surpassing previously reported MR values below one in the literature. These promising organomagnetic self-standing films hold significant potential for various future applications, including magnetic switches, sensors, e-skin devices, transistors, and organic spintronic devices.