Neutron diffraction is the only experimental method that can directly measure the spatial orientation of magnetic moments of various magnetic atoms in crystals. Through neutron diffraction, it was found that the magnetic structures of some rare earth elements and their alloys exhibit non collinear characteristics. Figure 2 shows the magnetic structure characteristics of some rare earth elements. Each circular orbit represents a certain crystal plane, and the arrow represents the orientation of the magnetic moment or the component on the c-axis and plane.

The magnetic properties of rare earth elements are derived from 4f electrons, which are localized in the inner orbital near the atomic nucleus. Therefore, 4f electrons in atoms cannot exchange directly with 4f electrons in neighboring atoms. However, 4f electrons can polarize the wandering s electrons. This polarized s electron has an impact on the spin orientation of 4f electrons. As a result, an indirect Exchange interaction between 4f electrons in rare earth atoms was formed by using s electrons as the medium. This Exchange interaction model is called RKKY theory (composed of the first letter of the surnames of Ruderman, Kittel, Kasuya and Yosida).

The Exchange interaction integral (interaction energy size) calculated according to the above theory is the wave function of Atomic spacing (i.e. positive, negative). Considering that the magnetic moment is affected by anisotropy, the orientation in space will change periodically. In this way, the RKKY theory can better explain various situations of non collinear magnetic structures.

New magnetic structure

With the further research on the magnetism of Amorphous metal, some new magnetic structures (see demagnetism) have been found in some rare earth transition metal alloy magnetic films.

Scattered ferromagnetism

In some amorphous alloys (such as Y-Fe, Nd-Fe, etc.), the magnetic moments of each atom are taken as magnetic structures that deviate from the overall average direction to a certain extent.

Scattered Antiferromagnetism

It is a random Antiferromagnetism magnetic structure (such as TbAg alloy film).