Properties of nanoporous carbon with pores filled by Ni atoms

Using the electron spin resonance (ESR) method, conductance measurements, and small-angle X-ray scattering (SAXS), the properties of nanoporous carbon (NPC) containing atoms of Ni in the pores are studied in comparison with the nickel-free NPC studied before. Although the amount of Ni introduced into the nanopores is small, the NPC properties change significantly. The ESR spectra show that, at low temperatures, the charge carriers are captured at the localized states. The bulk ferromagnetism is not observed at temperatures as low as 3.2 K. Magnetic properties are strongly temperature dependent and are not limited by the paramagnetism of free charge carriers. The temperature dependence of the ESR resonance field indicates the influence of ferromagnetic inclusions. The ferromagnetic shift of the resonance fields is observed up to a temperature of 80 K. The temperature dependence of the conductance reveals an exponential growth with the activation energy close to those obtained from the ESR measurements. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)