Magnetism of purified amorphous carbon

Abstract

In this work, magnetic properties of activated carbon coal, which is also named amorphous carbon, were investigated. Composition and structure analysis was performed by XRD, SEM and EDS techniques. Position and width of peaks on XRD pattern confirmed amorphous structure of coals with small degree of graphitization. Magnetic measurements were performed by SQUID magnetometer. According to thermomagnetic measurements, in part of the samples, antiferromagnetic transition was observed near 120 K. Nature of such phenomena, as well as effect of oxygen and magnetic contaminations on thermomagnetic measurements are discussed referring to similar results from previous researches and data from literature.

The Structure and ferromagnetism of carbon nanofibers from polyacrylonitrile/ polyvinylpyrrolidone

“…Thus, we suggest that the origin of the ferromagnetism be attributed to the mixture of carbon atoms with sp 2 and sp 3 bonds according to the above XPS and Raman analysis, and this creates vacancies in the presence of unpaired electron spins in sp 3 carbon bonds that contribute the ferromagnetism [7,63]. In addition, the FE-SEM showed the smallest average diameter of nanofibers were possible magnetically ordered due to the large amount of graphitized carbons edge sites magnetism [18,64]. The observed ferromagnetism could be based on the rich carbon defects of carbon dangling bonds and strong ferromagnetic coupling between them [3].…”

“…Ferromagnetism in carbon exhibiting spontaneous magnetization at room-temperature was reported as early as 1987 [5]. There have been a number of publications in which reproducible observations of room-temperature magnetic ordering in different carbon allotropes, such as graphite [6][7][8][9], graphene [10], proton-irradiated highly oriented pyrolytic graphite (HOPG) [6,[11][12], carbon nanotubes [13][14][15], polymerized fullerenes [16], carbon nanofoam [17] and amorphous carbon [18] were reported. In addition, Ma et al [19] suggested the observation of room temperature ferromagnetism in a polymer which includes Teflon tape subjected to simple mechanical stretching, heating, or cutting.…”

Structure and Ferromagnetism in Carbon Nanofibers from PAN/PVP

“…Figure 3 shows the XRD pattern of all samples used for investigation of their crystal structures. For all samples, diffraction peaks corresponding to the (002) and ( 101) peaks of graphitic carbon were observed at approximately 2θ = 25° and 44° [20]. The broad diffraction peaks suggest the disorder and amorphous characteristics of the materials [32].…”

“…Furthermore, the carbon atoms neighboring to defects in samples will adjust their bonds to accommodate the defects and produce dangling sp 2 bonds, which generates a magnetic moment. Thus, the origin of the ≡ ferromagnetism was suggested to be attributed to the mixture of carbon atoms with sp 2 and sp 3 bonds according to the above XPS and Raman analysis, and this creates vacancies in the presence of unpaired electron spins in sp 3 carbon bonds that contributed the ferromagnetism [10,54], In addition, the FE-SEM shows the smallest average diameter of nano bers were possible magnetically ordered due to the large amount of graphitized carbons edge sites magnetism [20,55]. The observed ferromagnetism could be based on the rich carbon defects of carbon dangling bonds and strong ferromagnetic coupling between them [3].…”

“…Ferromagnetism in carbon exhibiting spontaneous magnetization at room-temperature was formerly reported as early as 1987 [9]. There have been a number of publications appearing in which reproducible observations of the room-temperature magnetic ordering in different carbon allotropes, such as graphite [5,[10][11][12], graphene [13], proton-irradiated highly oriented pyrolytic graphite (HOPG) [5,14,15], carbon nanotubes [6,16,17], polymerized fullerenes [18], carbon nanofoam [19] and amorphous carbon [20] were reported. In addition, Ma et al [21] suggested the observation of room temperature ferromagnetism in a polymer which includes Te on tape subjected to simple mechanical stretching, heating or cutting.…”