Magnetic properties and exchange bias behavior of poly(4-(octyloxy) phenyl-5- (thiophen-3-yl)-2-naphthoate): Insights from temperature-dependent magnetization and EPR spectroscopy

The polymer POPTN was investigated to elucidate its magnetic and optoelectronic properties, with particular emphasis on charge carrier mobility, dichroic behaviour, and magnetic interactions. Electron paramagnetic resonance (EPR) studies confirmed delocalization over the naphthalene side chains, contributing to the observed paramagnetic behaviour at room temperature. Temperature-dependent magnetic studies revealed paramagnetic behaviour at higher temperatures transitioning to weak ferromagnetism below 10 K. Curie-Weiss analysis indicated antiferromagnetic (AFM) coupling with a paramagnetic Curie temperature (θP) of -203 K. Exchange bias (EB) measurements demonstrated a significant hysteresis loop shift at 2 K, diminishing with increasing temperature and vanishing near 20 K. The maximum exchange bias field (HE) was observed to be 133 Oe at 2 K, attributed to the coexistence of ferromagnetic (FM) and AFM interactions. The interplay of AFM and FM coupling, along with π-π stacking facilitated by the naphthyl moiety, influenced the magnetic properties and anisotropy. Bull. Chem. Soc. Ethiop. 2025, 39(4), 791-798. DOI: https://dx.doi.org/10.4314/bcse.v39i4.14