Magnetism in oxidized graphenes with hydroxyl groups

Abstract

The magnetic properties of three oxidized graphene structures with hydroxyl groups (cases A, B and C) have been investigated through spin-polarized density functional theory. The results reveal that in a graphene hexagonal ring structure, chemical bond formation by two non-neighbored hydroxyl-bonded carbon atoms with one carbon atom between (case B) can cause unpaired spins to produce a magnetic moment of 1.2 μ(B), while chemical bond formation by two neighbored hydroxyl-bonded carbon atoms (case A) or non-neighbored hydroxyl-bonded carbon atoms with two carbon atoms between (case C) cannot generate unpaired spins for nonmagnetic states. These magnetic oxidized graphenes have great promise for new spintronics. This work provides fundamentals to controllably synthesize or/and oxidized graphene with hydroxyl groups at specific carbon positions for magnetic properties.

Robust magnetic moments on the basal plane of the graphene sheet effectively induced by OH groups

“…However, the vacancies and edges generated by annealing GO are disordered 46 , and dangling bonds terminated by oxygen groups (such as carbonyl or ether) 6 47 , the unavoidable emergence of double vacancies, Stone-Wales defects, and so on, would lead to nonmagnetic states reconstruction 12 . Based on the theoretical predictions that OH groups can induce robust magnetic moments on the basal plane of graphene 6 27 28 31 and our experimental evidence of very high intrinsic magnetization, one can conclude that OH groups are the mainly magnetic source of aGO and the OHG samples.…”

“…It is known that (i) epoxy is nonmagnetic for it creates equal defects in A and B sublattice 4 , by contrast, a single OH group can induce ~1 μ B on the basal plane of the graphene sheet 6 27 28 ; and (ii) epoxy is thermally unstable and can be easily removed by annealing, leaving only stable OH groups on the basal-plane sites 34 35 36 37 . Therefore, to increase the magnetization of aGO for clarifying the magnetic contribution of OH groups, we synthesized the OHG samples by annealing aGO at different temperatures.…”

“…Recently, theoretical studies confirmed that the chemisorption of a single OH group on the basal plane of graphene can introduce magnetic moment ~1 μ B 6 27 28 . But the great difference is, not like F or H adatoms clustering 6 8 20 , OH groups on graphene sheet can be stable because of the suitable binding energy and relatively high migration barrier of C–OH bond 6 29 30 31 .…”

Realization of ferromagnetic graphene oxide with high magnetization by doping graphene oxide with nitrogen

“…Especially, the O content is relatively high, and the difference of O contribution in GO and NGO is highly possible3839. Approximately, to make a simple comparison with the results of NGO, we obtained GO samples (GO-a300, GO-a500, GO-a700, and GO-a900, numeric numbers denote the annealing temperature) by annealing GO in Ar.…”

Printable Giant Magnetoresistive Devices

“…However these composites exhibits small conductivity (∼10 −7 S/m) with resistances for micrometre sized structures in the range of 10 9 Ohm, which is unacceptably high for printable electronics 20, 21. In addition to the spintronics based on magnetic multilayers, recent theoretical works are dealing with alternatives based on graphene 22, 23. However, no experimental demonstrations with respect to printable graphene‐based magnetic sensorics are known at present.…”