Unusual broad antiferromagnetic transition in weakly graphitic carbon foam continuously filled with α-Fe

Ferromagnetically filled graphitic-carbon foams are a new class of materials characterized by an open-cell structure continuously filled with ferromagnetic crystals. In this work we report the novel observation of an unusual carbon phase nucleated on the surface of the iron filling after annealing for timescales of ~ 15 h at T~990 ºC. TEM and HRTEM profile analyses together with fast Fourier transform (FFT) allowed for the identification of a distorted graphite structure. Extended structural investigation carried out by employing point- and spatial-mapping Raman spectroscopy (excitation wavelength of 633 nm) revealed particularly intense and broad D bands and a generally weak G band. T-ESR signals acquired at T~ 300 K, 200 K,150 K, 100 K and 77 K further revealed a gradual depletion in the amplitude of the π-electron differential absorption feature, indicative of a progressive antiferromagnetic transition.