Spanish physicists have discovered that local magnetic moments can be created in graphite by removing individual atoms on the surface of the graphite material and creating atomic vacancies. This research contributes to the development of new methods for making magnets using non-metallic materials and biocompatible materials, and is lighter and less expensive than existing magnets.
The study was completed by the Autonomous University of Madrid and the research group of the Madrid Institute of Materials Science, and the relevant paper was published in the recently published Physics Review Letter. In the experiment, the researchers used high-order pyrolytic graphite, which was formed by stacking graphene layers in accordance with the AB-AB pattern. They first removed some of the A-layer graphene in an ultra-clean environment to ensure that the surface of the graphite was completely free of impurities; then the low-energy ionizing radiation was used to displace the atoms of the surface to create an atomic vacancy.
Through a self-made cryogenic scanning tunneling microscope, the team found that the sharp resonance peak of the Fermi level appeared at the top of each atomic vacancy. Many theoretical studies have predicted this phenomenon, but this is the first observation through experiments. .
The researchers explained that the resonance of each atomic vacancy corresponds to a magnetic moment because there is a repulsive interaction between electrons and electrons, and the atomic vacancies cause the electron spins around them to line up to form a magnetic moment. Moreover, vacancies in different locations produce different magnetic moments, and the magnetic moments also interact with each other, so that the individual graphite materials can be removed with a single carbon atom to make the entire graphite material visible to the naked eye.
Ivan Briucha, who participated in the study, said that ordinary carbon-based materials usually do not exhibit magnetic force because the electrons in them are combined by covalent bonds, and the total spin of the electrons is zero. The net magnetic moment cannot exist. Once a carbon atom is removed from the surface of the graphite, the electron pair bound by the covalent bond is broken and a single electron produces a local magnetic moment.
This result not only confirms the accuracy of the theoretical model, but also has many deep meanings. For example, observed resonances may enhance the chemical reactivity of graphite; in applications, this technology may be used to make innovative non-metallic materials, with good prospects in the electronics and biomedical fields. In addition, graphite magnets are cheaper to manufacture than conventional magnets. The price of 1 ton of carbon is less than one-thousandth of the price of nickel, and graphite magnets have the advantages of light weight and good elasticity. However, to date, the magnetic properties of the reported graphite magnets are not far behind the most powerful magnets available.
Brishoga said that creating atomic vacancies by removing atoms in graphene-like materials can have a major impact on the mechanical, electrical, and magnetic properties of materials, and one of the pressing challenges facing nanotechnology today is How to integrate graphite into real electronic devices, the brightest future of this experiment is applied to rotating electronics research, which is to develop a new generation of electronic devices through the spin of unpaired electrons. Â
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