Detecting bulk carbon ferromagnetism in graphene multi-edge structure
arxiv(2023)
摘要
The emergence of bulk carbon ferromagnetism is long-expected over years. At
nanoscale, carbon ferromagnetism was detected by analyzing the magnetic edge
states via scanning tunneling microscopy(STM), and its origin can be explained
by local redistribution of electron wave function. In larger scale, carbon
ferromagnetism can be created by deliberately producing defects in graphite,
and detected by macroscopic technical magnetization. Meanwhile, it becomes
crucial to determine that the detected magnetization is originated from carbon
rather than from magnetic impurities. One solution is X-ray magnetic circular
dichroism (XMCD). Nonetheless, a reproducible, full section of XMCD spectrum
across C-1s absorption energy has not appeared yet, which should be decisive
for assuring the indisputable existence of bulk carbon ferromagnetism. Besides,
the lack of direct observation on the atomic structure of the ferromagnetic
carbon leaves the structural origin of its ferromagnetism still in mist. In
this work, for detecting bulk carbon ferromagnetism, we managed to grow
all-carbon film consisting of vertically aligned graphene multi-edge (VGME),
which wove into a three-dimensional hyperfine-porous network. Magnetization
(M-H) curves and XMCD spectra co-confirmed bulk carbon ferromagnetism of VGME
at room temperature, with the average unit magnetic momentum of 0.0006
miuB/atom. The influence of magnetic impurities on magnetization was excluded
by both absorption spectra and inductively coupled plasma mass spectrometry
measurements. The spin transfer behavior also verified the long-range and
robust feature of the bulk carbon ferromagnetism. Our work provides direct
evidence of elementary resolved bulk carbon ferromagnetism at room temperature
and clarifies its origin from pi-electrons at graphene edges.
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