Possible room-temperature ferromagnetism in hydrogenated carbon nanotubes

Abstract

We find that ferromagnetism can be induced in carbon nanotubes (CNTs) by introducing hydrogen. Multiwalled CNTs grown inside porous alumina templates contain a large density of defects resulting in significant hydrogen uptake when annealed at high temperatures. This hydrogen incorporation produces H-complex and adatom magnetism which generates a sizeable ferromagnetic moment and a Curie temperature near T C =1000 K. We studied the conditions for the incorporation of hydrogen, the temperature-dependent magnetic behavior, and the dependence of the ferromagnetism on the size of the nanotubes.

Room temperature ferromagnetism in Teflon due to carbon dangling bonds

“…Spin flip excitation is considered near Curie temperature and the Ising model provides a better description for spin flip excitation. It is unequivocal that the theoretical model (red curve) from the conjunction of spin-wave theory and the Ising model fit the measured data well with Curie temperature of ~680 K. It should be noted that the high Curie temperature is in consistence with those reported in carbon nanostructures (that is, 1,000 K for carbon nanotubes, 764 K for graphene and 460 K for graphite) [7][8][9] . On the basis of the above discussion, the disappearance of FM at 340-350 °C (613-623 K) can be attributed to melting of Teflon.…”

Structural Defects in Graphene

“…The driving force behind these studies was not only to create technologically important, light, nonmetallic magnets with a Curie point well above room temperature, but also to understand a fundamental problem: the origin of magnetism in a system which traditionally has been thought to show diamagnetic behavior only. In addition to polymerized fullerenes, 120 nanotubes, 121 graphite, 122 and nanodiamonds, 123 magnetism was recently reported for graphene produced from graphene oxide. 124 On the basis of calculations, the observed magnetic behavior in all these systems was explained in terms of defects in the graphitic network (either native or produced by ion irradiation) such as under-coordinated carbon atoms, for example, vacancies, 125 interstitials, 126 carbon adatoms, 47 and atoms at the edges of graphitic nanofragments with dangling bonds either passivated with hydrogen atoms or free.…”

Homoepitaxial graphene tunnel barriers for spin transport

“…28 Hydrogenated graphene devices do not show as high a spin polarization value, even though the value is still higher than most oxide tunnel barrier devices. 29 This could possibly be due to scattering introduced by theoretically predicted 30,31 and experimentally verified 32,33 magnetic moments in hydrogenated graphene. Figure 5 shows the bias dependence for of the spin lifetime for both the fluorinated graphene/ graphene and hydrogenated graphene/graphene devices.…”