Silicon steel plate
Excels in the low frequency range, and is often used in power transformers and choke coils in the commercial frequency range (50/60 Hz). The magnetic permeability increase and aging can be reduced by having a few percent of silicon in iron. This material is then cold-rolled into a sheet of approximately 0.05 ~ 0.5 mm thickness, punched into an E-shape I, and several 10 sheets are stacked on top of each other.
The iron core surface is insulated one by one to suppress the loss due to eddy current. The higher the frequency is, the thinner the thickness should be.
Permalloy
Material with high permeability made by adding nickel to iron. By changing the nickel content, the initial permeability and saturation magnetic flux density change, so it is used for low frequency signal transformers, choke coils, etc.
Dust core
Formed by compression molding of fine particles of molybdenum as the main component. The loss due to eddy current can be reduced compared to using silicon steel sheet since the magnetic resistance is higher. It is used in power line filters and high frequency smoothing coils for switching power supplies.