Preparation of ferromagnetic pyrolytic carbon by heating under magnetic field and its physical properties

以三乙胺为原料，在高达6特斯拉的高磁场下热解制备了热解碳样品，并对其磁性能进行了研究。热解产物在室温下也能获得铁磁性样品。300K时的最大自发磁化强度为3.0 emu/g。用同步x射线衍射实验对晶体结构进行了研究。在铁磁样品中观察到金刚石的衍射峰。因此，自由基自旋的铁磁有序可能是由金刚石结构中的缺陷引起的。制备过程中，金刚石的衍射峰强度随外加磁场的增大而增大。因此，磁场可能有助于在碳基铁磁体中形成三维铁磁结构。在6特斯拉的磁场下，用金刚石粉进行现场热解，得到了300K下磁化强度为6.4emu/g的铁磁样品。铁磁热解碳在金刚石粉上可以加速晶体生长，这与上述同步加速器x射线衍射结果一致。

We have prepared pyrolytic carbon samples from triethylamine by pyrolysis under high magnetic field up to 6 Tesla, and investigated their magnetic properties. Ferromagnetic samples were obtained from the pyrolysis products even at room temperature. The maximum spontaneous magnetization was 3.0 emu/g at 300K. The crystal structure was examined by the synchrotron X-ray diffraction experiment at SPring-8. The diffraction peak of diamond was observed for the ferromagnetic samples. Thus, it is possible that the ferromagnetic ordering of radical spins is caused by defects in the diamond structure. The diffraction peak intensity of diamond for the ferromagnetic samples increased with the applied magnetic field at sample preparation. Therefore, the magnetic field may help to form a three dimensional ferromagnetic structure in the carbon-based ferromagnet. A ferromagnetic sample with higher magnetization of 6.4emu/g at 300K was also obtained by field-pyrolysis with diamond powder under magnetic field of 6 Tesla. The crystal growth of the ferromagnetic pyrolytic carbon may be accelerated on the diamond powder, which is consistent with the above-mentioned synchrotron X-ray diffraction result.