1) Organic compounds: Most of them are conjugated macrocyclic organic radicals containing unpaired electrons. The first magnetic organic compound, Galvinoxyl [1], is characterized by low density, but the ground state spin S cannot be very high, otherwise it is unstable, and therefore its magnetism is weak.

The first magnetic organic compound, Galvinoxy

(2) Molecular polymers: mainly low dimensional polymers such as C60 derivatives. The magnetism of such compounds may be derived from Delocalized electron, and the magnetism is also weak and not stable enough. It has been confirmed that the strong magnetism of C60 reported once actually comes from Fe3C generated during the synthesis of C60 [4].

(3) Complex: It is a type of compound formed by organic ligands surrounding metals. This type of material has the characteristics of both inorganic and organic materials. As long as the molecular design is reasonable, the structure and properties of magnets can be controlled by adjusting different ligands. The magnetism of complexes mainly comes from central metal ions with large spin S, which can provide much stronger magnetism than pure organic materials. It is a focus of research on molecular based magnetic materials, When dealing with the interaction between components with spin Quantum number Si in the molecular magnetic system under the magnetic field H, the phenomenological spin equivalent operator method is adopted in physics, and its Hamiltonian operator is expressed as: H ^ s=g β S ^ · H+S ^ · D · S^+ Σ Ji, jS ^ i · S ^ j, (2)

The first term is the Zeeman effect under magnetic field H, where g is the Lande factor, β Is Bohr magneton; The second term is Zero field splitting caused by spin orbit coupling or low symmetry field, and D is called Zero field splitting parameter; The third term is the magnetic coupling between the spin component Si and Sj in the molecule, Jij is called the Coupling constant