Magnetic transitions in graphene derivatives

The magnetic transitions in graphene oxide （GO） have been investigated experimentally. Micron-sized GO flakes exhibit dominant diamagnetism accompanied by weak ferromagnetism at room temperature. However, when the lateral dimensions of GO flakes are reduced from micron-size to nano-size, a clear transition from dominant diamagnetism to ferromagnetism is observed. After reducing the GO chemically or thermally, the dominant magnetic properties are not altered markedly except for the gradual enhancement of ferromagnetic components. In contrast, at 2 K, significant paramagnetism is present in both the micron-sized and nano-sized GO sheets. The effects of different functional groups on magnetic transitions in graphene derivatives have been further investigated using on hydroxyl-, carboxyl-, amino- and thiol- functionalized graphene. The results reveal that significant diamagnetism with weak ferromagnetism is present at room temperature in all of these functionalized graphene derivatives and the ability of different functional groups to introduce magnetic moments follows the order -SH 〉 --OH 〉 -COOH, -NH2. Notably, at 5 K, diamagnetism, paramagnetism and ferromagnetism coexist in thiol-, hydroxyl- and carboxyl-functionalized graphene, while amino-graphene exhibits dominant paramagnetism, analogous to the low-temperature magnetism in GO. These results indicate that diamagnetism, paramagnetism and ferromagnetism can coexist in graphene derivatives and magnetic transitions among the three states can be achieved which depend on edge states, vacancies, chemical doping and the attached functional groups. The results obtained may help settle the current controversy about the magnetism of graphene-related materials.

在 graphene 氧化物的磁性的转变(去) 试验性地被调查了。微米大小去薄片展出弱强磁性在房间温度伴随的主导的抗磁性。不管多么侧面的尺寸去薄片从微米尺寸被归结为 nano 尺寸，到强磁性的从主导的抗磁性的清楚的转变被观察。在化学上或热地减少 GO 以后，主导的磁性没除了铁磁性的部件的渐渐的改进显著地被改变。相反在 2 K，重要常磁性在两个是在场的微米大小、缩放 nano 去表。在 graphene 衍生物的磁性的转变上的不同的功能的组的效果进一步被调查了在氢氧根上使用 -- ， carboxyl- ，氨基 -- 并且 thiolfunctionalized graphene。结果表明有弱强磁性的那重要抗磁性在在所有这些 functionalized graphene 衍生物和不同的功能的组的能力的房间温度是在场的介绍磁性的时刻嘘跟随顺序 > 哦 >-COOH,-NH 2 。尤其是，在 5 点， K，抗磁性，常磁性和强磁性在 thiol- 共存， hydroxyland carboxyl-functionalized graphene 当 amino-graphene 展出主导的常磁性时，类似于低温度的磁力在去。这些结果显示那抗磁性，常磁性和强磁性能在三个状态之中在 graphene 衍生物和磁性的转变共存能被完成它取决于边状态，空缺，化学的做和依附的功能的组。获得的结果可以帮助关于 graphene 相关的材料的磁力解决当前的争吵。