If you need high magnetic output in the very small space, the NdFeB is the first choice. It is widely used in the micro electronic products, sensor and compact components. This application need small size magnet to achieve high magnet performance. Meanwhile, Compared to the other material, the NdFeB is more sensitive to the corrosion and temperature. So we need to consider the surface coating and working scenario.
The SmCo is normally used in the high standard application to the temperature stability and anti corrosion. It the reliable micro component which is suitable to run in the critical environment. Compared with the NdFeB magnet, the SmCo is normally low magnetic output in the room temperature. However when the heat stability and long time reliability is more important, SmCo is the better choice.
The ferrite magnet applied in the application scenario which has high standard in cost control and low standard in the magnetic output. It has good anti corrosion and steady heat performance in many scenarios. Because the the magnetic force is lower of the ferrite magnet, it is not always used in the very tiny space in the application.
The Alnico is famous in the good temperature steability. It could used in same precision application. When you need wider working temperature range, you could choose the Alnico. However for some high coercivity and high demagnetized small magnet, Alnico is less used. Compared with the above four materials, FrCrCo could used in some micro magnet application. Even it is not very popular, when you have specified requirement, you could also use FeCrCo.
