Temperature dependences of paramagnetic response in oxidized spark plasma sintered carbon nanotubes: The way of understanding the local electronic structure

Abstract

Electron paramagnetic resonance (EPR) spectroscopy was used to study an electronic structure of carbon nanotubes (CNTs) consolidated by spark plasma sintering and additionally oxidized in vapor of boiling nitric acid. Two components were distinguished in the EPR absorption spectra: narrow and broad lines with different g-factors. This testified to the different surrounding of paramagnetic centers associated with the lines. Temperature dependence of spin numbers, associated with the narrow line, transfers from Curie-Weiss law to Curie law with increasing temperature. EPR susceptibility, associated with the broad line, can be attributed to a paramagnetic matrix with superparamagnetic inclusions.