Graphite has been confirmed to be non-magnetic at room temperature since it contains carbon atoms arranged in layers.
Despite this, graphite has various interesting properties, including its electric conductivity, similar to magnetic materials.
Graphite Vs. Diamagnetism
Materials that tend to repel an external magnetic field are termed diamagnetic. The repulsion comes from the motion of electrons inside material brought about by a field, which formulates their own small opposing magnetic field. Diamagnetism is not a property exhibited only by graphite.
Graphite is an allotropic form of carbon with a layered structure. Because of the structure of its electrons, graphite behaves like diamagnetic materials.
Its unique layered structure and weak interlayer bonding play a crucial role in influencing the overall magnetic response of the material.
Factors Affecting Graphite Magnetism
Interlayer Coupling (Hexagonal Lattice Structure)
The individual graphene layers in graphite are slightly diamagnetic. You will realize that there is a slight repulsion to magnetic fields. Yet, how these layers are stacked is critical.
The layers are bound together by weak van der Waals forces, and their relative orientation and spacing can affect their mutual magnetic interaction.
Impurities (Doping and Defects)
The electronic structure of graphene and its magnetic properties can be altered by introducing atoms (dopants) or creating structural defects.
By replacing one or more carbon atoms with elements such as boron or nitrogen, the system comes to contain unpaired electrons.
This makes it susceptible to ferromagnetism (where all its magnetic moments are oriented in a single direction).
External Magnetic Field
It turns out that even pure graphite, without any dopants or defects, can be induced to become a magnet by applying an external magnetic field. When one layer exists in each element, field alignment can orient drill layers and create a net macroscopic magnetization.
Temperature Variations
The magnetism of graphite is greatly affected by temperature. Temperature causes changes in the kinetic energy of its electrons.
At the same time, it alters their mobility, resulting in a change in magnetic properties. The influence of temperature helps explain the nature and changeability of graphite magnetism.
Structure of Graphite and Impacts on Magnetism
Honeycomb Layers
The graphene layers are like honeycombs, with carbon atoms in a tight sp2 hybrid structure and forming strong bonds within each layer.
These bonds make graphite a good conductor and restrict the movement of electrons over planes perpendicular to their direction. This confined movement is a key factor in preventing layers from interacting magnetically too strongly.
Weak Bonding Between Layers
Layers of graphene pile on top of one another, bound by weak van der Waals interactions. Because the in-plane sp2 bonds are much stronger than these interlayer forces, there is very little electronic interaction between layers.
This weak coupling lets each layer maintain its basic diamagnetism, a slight resistance to magnetic fields. Yet these layers’ relative positioning will affect their overall magnetic response.
Stacking Order and Magnetism
This interlayer magnetic interaction depends on the stacking sequence of layers in graphene stacks.
When two layers on Bernal stacking exhibit oppositely oriented diamagnetism, the effect is antiferromagnetic (the total magnetization cancels out).
The dance may be modified with other possible stacking patterns, resulting in weak ferromagnetism or exotic magnetic phenomena due to tiny changes affecting electron delocalization between layers.
Edge Effects and Defects
Finally, the edges of graphene sheets leave dangling bonds, producing local magnetic moments. These can then interact with the weak diamagnetism of the bulk and thereby affect overall magnetic behavior.
At times, you can add foreign atoms, such as boron or nitrogen, which bring unpaired electrons that contribute to stronger ferromagnetism.
Other Types of Carbon and their Magnetic Properties
Diamond
Made of a tetrahedral lattice, which gives it its appearance, this amazing feature makes it diamagnetic.
Because each carbon bonds equally with all four neighbors, the electrons are paired, and there is no net magnetic moment.
Yet nitrogen impurities or other surface irregularities can leave unpaired electrons, which weaken the ferromagnetism.
Fullerenes
Like the well-known buckyballs, these spherical or cylindrical carbon cages likewise exhibit diamagnetism.
In addition, their closed-shell electronic structure produces few unpaired electrons. But, by using magnetic atoms to dope or by attaching a magnetically moving molecule, doors can be opened for new nanomagnets.
Carbon Nanotubes
These one-dimensional marvels show different types of magnetic behavior under the influence of variations in chirality and diameter.
The metallic nanotubes are diamagnetic, but the semiconducting ones can be paramagnetic if they have unpaired electrons in their band structure.
Adding defects or impurities may cause ferromagnetism or antiferromagnetism, making them excellent candidates for spintronics.
Amorphous Carbon
In this disordered form, which contains soot and charcoal, the electron structure is randomized and delocalized; there’s little or no diamagnetism.
If impurities or defects are present, it introduces localized magnetic moments causing these materials to have very complex behavior.
Graphene
Although they are just as similar to graphite, independently formed graphene sheets have unusual quantum magnetism.
This is because of their being two-dimensional and increased electron-electron interactions. This paves new ways to research exotic magnetism at the atomic level.
Conclusion
This is just a glimpse into the captivating world of carbon magnetism. With ongoing research and exploration, we may discover fascinating magnetic secrets.
More Resource
Graphite melting point – KDMfab