The higher the order of arrangement of magnetic domains, the stronger the magnetism. Permanent magnetic materials have a stable arrangement of magnetic domains that can maintain a stable magnetic state over time. In contrast, soft magnetic materials can more easily change the arrangement of magnetic domains, resulting in a smaller remaining magnetism after magnetization.
Magnetic Domains and Magnetism
The magnetism of a magnet originates from “magnetic domains” within its internal microstructure. Magnetic domains are small regions within magnetic materials where the magnetization direction is uniform, and each domain acts like a tiny magnet. In a normal state, the domain magnetizations are chaotic, and their collective magnetization cancels out, making the magnet appear non-magnetic externally. When a magnet is magnetized, the external magnetic field gradually aligns the domains’ magnetization directions, resulting in a macroscopic magnetic effect.
Effects of Heating on the Arrangement of Magnetic Domains
When a magnet is heated, it absorbs heat, which intensifies the thermal motion of its internal atoms and electrons. At high temperatures, the increased vibrations of the atoms within the domains provide energy for changes in the domain directions. Once the temperature rises to a certain level, the ordered arrangement of the domains is completely disrupted, and their directions become chaotic again.
Influence of Impact on the Arrangement of Magnetic Domains
Impacting a magnet can lead to demagnetization; however, the effect is usually not complete and depends on the intensity of the impact and the material of the magnet.
| Strength of the Impact: The magnetism of a magnet comes from the ordered arrangement of its internal magnetic domains. A strong impact may disturb this arrangement, causing some domains to change direction and weaken the magnetism. However, to achieve complete demagnetization, the arrangement of the domains must be completely randomized, which is difficult to achieve through simple impact.
| Material of the Magnet: Different types of magnets have varying sensitivities to impact:
Soft Magnetic Materials (e.g., ferrite): The domains in these materials are more easily influenced by external factors, and an impact may significantly weaken their magnetism.
Hard Magnetic Materials (e.g., neodymium-iron-boron, samarium-cobalt): These magnets have high coercivity, making their domain arrangements more stable. Typically, impacts of regular strength fail to demagnetize them; however, repeated strong impacts or the breaking of the magnet may result in a decrease in magnetism.
Therefore, impacting can serve as an auxiliary method for demagnetization, but it usually requires the combination of other methods (such as heating or applying reverse magnetic fields) for complete demagnetization.
Effects of Reverse Magnetic Fields on the Arrangement of Magnetic Domains
When a sufficiently strong reverse magnetic field is applied, it opposes the originally existing directions of the magnetic domains within the magnet. As the intensity of the reverse magnetic field increases, the domains gradually rotate to follow the direction of the field. Once the intensity reaches a certain level, the arrangement of magnetic domains is thoroughly disrupted, returning to a chaotic state, and the macroscopic magnetism of the magnet dissipates, realizing demagnetization.
It is important to note that the effectiveness of demagnetization depends on the intensity and duration of the reverse magnetic field. Different materials may require different reverse magnetic field intensities and conditions for demagnetization. Some high-performance magnets, due to their high coercivity, may need stronger reverse fields for effective demagnetization.
Magnets Manufacturer
At Tengye, we’re thrilled to be early participants in your new projects. Our passion for magnets extends from material selection and design optimization to providing magnetic solutions. We hope to bring our knowledge and experience to the forefront by actively engaging in your upcoming projects. Work with our magnet experts to get the right magnet solution.
image source: electronics-tutorials & gstatic & kjmagnetics & web & mdpi & topmag
