I. By measuring magnetic parameters under different environmental conditions

1. Magnetic measurement under temperature changes

(1) Principle:

The magnetism of amorphous nanocrystalline materials is sensitive to temperature. As the temperature increases, the thermal motion of atoms inside the material intensifies, which will affect the orderly arrangement of magnetic moments, thereby changing the magnetic parameters. For example, the Curie temperature (Tc) is the key temperature point at which the material's magnetism transitions. When the temperature approaches or exceeds the Curie temperature, the material's ferromagnetism disappears.

(2) Measurement methods and evaluation:

Use variable temperature magnetic measurement equipment, such as a vibrating sample magnetometer (VSM) or a superconducting quantum interferometer (SQUID) equipped with a heating or cooling device, to measure the magnetization (M) of a material as a function of a magnetic field (H) at different temperatures. changing relationships. Observe the change curve of magnetization intensity with temperature. If the change of magnetization intensity is relatively gentle in a certain temperature range, it means that the material has good stability in this temperature range; if the magnetization intensity drops sharply or changes abnormally, it means that the material has good stability. The stability is poor. In addition, stability can also be evaluated by measuring the magnetic permeability at different temperatures. Stable materials have smaller changes in magnetic permeability within a certain temperature range.

2. Magnetic measurement in humidity environment

(1) Principle:

Humidity may cause water adsorption or chemical reactions on the surface of amorphous nanocrystalline materials, thereby affecting the microstructure and magnetism of the materials. For example, moisture adsorption may cause oxidation of the material surface and change the magnetic anisotropy of the material surface.

(2) Measurement methods and evaluation:

Magnetic measurements are taken after the material has been exposed to different humidity environments for a period of time (e.g. via a humidity control box). The hysteresis loop can be measured and compared with changes in parameters such as the shape of the hysteresis loop, coercive force and residual magnetization under different humidity environments. If the changes in these parameters are small, it means that the material has good stability when humidity changes; otherwise, the stability is poor.

3. Magnetic measurement under the long-term effect of external magnetic field

(1) Principle:

Long-term application of an external magnetic field may cause irreversible changes in the magnetic domain structure inside the amorphous nanocrystalline material, thereby affecting the magnetism. If the material has good stability, its magnetism should be able to return to its original state or change very little after the external magnetic field is removed.

(2) Measurement methods and evaluation:

A constant external magnetic field of a certain intensity is applied to the material for a period of time (ranging from hours to months, depending on the material's application scenario and expected stability requirements). After that, the external magnetic field is removed, and the magnetic parameters of the material, such as magnetization intensity, magnetic permeability, etc., are measured and compared with the initial values before the external magnetic field is applied. If the changes in magnetic parameters are within the acceptable range, it indicates that the material has good stability under the action of a long-term external magnetic field.

II. Measurement based on magnetic relaxation phenomena

1. Magnetic aftereffect measurement

(1) Principle:

After the amorphous nanocrystalline material is subjected to a change in the magnetic field, its magnetization intensity will not reach a stable value immediately, but will take a certain amount of time to relax to the final state. This phenomenon is called magnetic aftereffect. The magnetic aftereffect is related to the microstructure, atomic diffusion and other factors inside the material. The stability of the material can be reflected by measuring the magnetic aftereffect.

(2) Measurement methods and evaluation:

Use time-resolved magnetic measurement techniques, such as pulsed magnetic field technology combined with fast-response magnetic measurement instruments. When a pulsed magnetic field is applied, the magnetization intensity is measured as a function of time. If the magnetic aftereffect of the material is small, that is, the magnetization can quickly relax to a stable value, and the relaxation process conforms to the expected law (such as the exponential decay law), it means that the material has good stability. On the contrary, if the magnetic aftereffect is large and the relaxation process is abnormal (such as long-term fluctuations or non-exponential decay), it may indicate the existence of unstable factors within the material, such as microstructural defects or composition inhomogeneity.

2. Frequency dependence measurement

(1) Principle:

Under the action of an alternating magnetic field, the magnetism of amorphous nanocrystalline materials will show frequency dependence. This frequency dependence is related to processes such as magnetic domain wall motion and spin relaxation inside the material. For a stable material, within a certain frequency range, the frequency dependence of its magnetic parameters (such as magnetic permeability, loss tangent, etc.) should comply with certain laws and have small changes.

(2) Measurement methods and evaluation:

Use magnetic measurement equipment capable of producing alternating magnetic fields of different frequencies, such as an AC susceptibility meter or impedance analyzer. The magnetic parameters of the material are measured as a function of frequency over a wide frequency range (for example, from tens of Hz at low frequencies to several megahertz at high frequencies). If the material's magnetic parameters show smooth changes in this frequency range and are consistent with theoretical models or the behavior of known stable materials, it indicates that the material has good stability. If abnormal peaks, valleys or mutations appear at certain frequency points, it may indicate a stability problem in the material. For example, it may be due to the coupling between different phases within the material or the inhomogeneous microstructure.