Study of physical properties of a ferrimagnetic spinel CuMnO: spin dynamics, magnetocaloric effect and critical behavior.

The present work reports a detailed study of the spin dynamics, magnetocaloric effect and critical behaviour near the magnetic phase transition temperature, of a ferrimagnetic spinel CuMnO. The dynamic magnetic properties investigated using frequency-dependent ac magnetic susceptibility fitted using different phenomenological models such as Neel-Arrhenius, Vogel-Fulcher and power law, strongly indicate the presence of a cluster-glass-like behavior of CuMnO at 40 K. The magnetization data have revealed that our compound displays an occurrence of second-order paramagnetic (PM) to ferrimagnetic (FIM) phase transition at the Curie temperature = 80 K as the temperature decrease.

Poly[2,2'-(4,4'-bipyridine)-5,5'-bibenzimidazole] functionalization of carbon black for improving the oxidation stability and oxygen reduction reaction of fuel cells.

The rapid oxidation of carbon black (CB) is a major drawback for its use as a catalyst support in polymer electrolyte fuel cells. Here, we synthesize poly[2,2'-(4,4'-bipyridine)-5,5'-bibenzimidazole] (BiPyPBI) as a conducting polymer and use it to functionalize the surface of CB and homogenously anchor platinum metal nanoparticles (Pt-NPs) on a CB surface. The as-prepared materials were confirmed by different spectroscopic techniques, including nuclear magnetic resonance spectroscopy, energy-dispersive X-ray, thermal gravimetric analysis, and scanning-transmittance microscopy.