|Soft and Hard Magnetic Materials
For understanding the hard magnetic materials, we have to know certain terms. They are as follows:
Now, we can define hard magnetic materials. These materials are really hard in the basis that it is very difficult to get magnetised. The reason is that the domain walls are motionless owing to crystal defects and imperfections.
But if it gets magnetised, it will be permanently magnetised. That is why; it is also called as permanent magnetic material. They have coercive force greater than 10kA/m and have high retentivity. When we expose a hard magnet to an external magnetic field for the first time, the domain grows and rotates to align with the applied field at the saturation magnetization. After that, the field is removed. As a result, the magnetization is somewhat reverted but it does not track the magnetization curve any longer. A certain amount of energy (Br) is stored in the magnet and it becomes permanently magnetized.
Properties of Hard Magnetic Materials
The properties of some important permanent magnetic material are shown in the table below.
Some important hard magnetic materials are the following:
Nanocrystalline hard magnet (Nd-Fe-B Alloys):