Macroscopic behavior and microscopic magnetic properties of nanocarbon

Here are presented investigations of powder and glass-like samples containing carbon nanoparticles, not intentionally doped and doped with Ag, Au and Co. The neutron diffraction study reveals an amorphous structure of the samples doped with Au and Co, as well as the magnetic scattering due to a long-range FM order in the Co-doped sample. The composition and molecular structure of the sample doped with Au is clarified with the NMR investigations. The temperature dependence of the magnetization, M (T), exhibits large irreversibility in low fields of B=1–7mT. M (B) saturates already above 2T at high temperatures, but deviates from the saturation behavior below ~50 (150K). Magnetic hysteresis is observed already at 300K and exhibits a power-law temperature decay of the coercive field, Bc (T). The macroscopic behavior above is typical of an assembly of partially blocked magnetic nanoparticles. The values of the saturation magnetization, Ms, and the blocking temperature, Tb, are obtained as well. However, the hysteresis loop in the Co-doped sample differs from that in other samples, and the values of Bc and Ms are noticeably increased. •We have investigated powder and glassy samples with carbon nanoparticles.•They include an undoped sample and those doped with Ag, Au and Co.•Neutron diffraction study reveals amorphous structure of Au- and Co-doped samples.•Composition and molecular structure of Au-doped sample was investigated with NMR.•Magnetic behavior is typical of an assembly of partially blocked magnetic nanoparticles.