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Magnetic moment manipulation in hydrogen-peroxide-doped grafoil, pyrolytic graphite and Fe3C-filled multiwall carbon nanotubes
Nano Express ( IF 2.7 ) Pub Date : 2020-11-26 , DOI: 10.1088/2632-959x/abc908
Mahsa Fayazi 1 , Gao Shuai 1 , Li Lei 2 , Yi He 3 , Filippo S Boi 1
Affiliation  

Observation of granular superconductivity and percolative ferromagnetism in hydrogen/oxygen doped graphite materials has motivated recent research because of the unexplored scenarios in the field of magnetic-devices and spintronics. Here we report a novel investigation of the effects of hydrogen-peroxide-doping on the magnetic properties of grafoil, highly oriented pyrolytic graphite (HOPG) and carbon nanotube (CNT) samples characterized by specific defective characteristics. ZFC and FC magnetic curves acquired on the undoped boundary-defect-rich grafoil samples from 2 K to 300 K, revealed a spin-glass-like behaviour, with magnetic irreversibilities indicating the existence of percolative ferromagnetism. An enhancement in such effect was found in the post-doped samples below ∼70 K, together with a magnetic transition. This was evidenced further by ESR, with the appearance of a broad differential absorption peak at 77 K for g∼3.54, compatible with antiferromagnetic ordering in presence of ferromagnetic multilayers. An analogous enhancement of ferromagnetic signals was found on sp3-defect-rich HOPG, with the appearance of localized ESR differential absorption features at g factors of∼2.14, ∼2.08, ∼2.02,∼1.91 and∼1.86 at 77 K. Instead, comparisons performed in vacancy-rich doped CNTs revealed a significantly different trend, with an anomalous demagnetization of both the vacancy-rich graphitic CNT layers and encapsulated Fe3C nanowires. These observations seem to highlight a possible role of specific defects towards modifications of magnetic correlation in presence of hydrogen/oxygen species.



中文翻译:

掺杂过氧化氢的重油,热解石墨和Fe 3 C填充的多壁碳纳米管中的磁矩操纵

氢/氧掺杂石墨材料中颗粒超导性和渗透铁磁性的观察,由于在磁性器件和自旋电子学领域的未曾探索过的情况,已经推动了最近的研究。在这里,我们报告了对过氧化氢掺杂对以特有缺陷特征为特征的薄板油,高取向热解石墨(HOPG)和碳纳米管(CNT)样品的磁性的影响的新颖研究。在2 K至300 K的未掺杂富集边界缺陷的grafoil样品上获得的ZFC和FC磁曲线显示出类似自旋玻璃的行为,磁不可逆性表明存在渗透铁磁性。在低于70 K的后掺杂样品中发现这种效应的增强,并伴有磁跃迁。ESR进一步证明了这一点,在77 K处出现一个宽泛的差分吸收峰(g约为3.54),与存在铁磁多层体时的反铁磁有序性相容。在sp上发现铁磁信号的类似增强富含3缺陷的HOPG,在77 K时g因子为〜2.14,〜2.08,〜2.02,〜1.91和〜1.86时出现局部ESR差异吸收特征。相反,在富含空位的掺杂CNT中进行的比较显示出大量空位的石墨碳纳米管层和封装的Fe 3 C纳米线都发生了异常退磁。这些观察似乎突出了特定缺陷在存在氢/氧物种的情况下对改变磁相关性的可能作用。

更新日期:2020-11-26
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