Generally, permanent magnets can be divided into two major categories: the first category is metal alloy magnets, including neodymium magnets (Nd2Fe14B), samarium cobalt magnets (SmCo), aluminum nickel cobalt magnets (ALNiCO); the second category is ferrites or ceramic magnets. In our last article, we have written about what is an ALNiCO magnet. So in this article, we will introduce what is a ferrite.
The ferrite is a new type of non-metallic magnetic material developed in the 1940s. It is a metal oxide with ferrimagnetism. In terms of electrical characteristics, the resistivity of ferrite is much larger than that of a single metal or alloy magnetic materials, and it also has higher dielectric properties. The magnetic properties of ferrite are also manifested in high magnetic permeability at high frequencies. Therefore, ferrite has become a widely used non-metallic magnetic material in the field of high-frequency weak current.
Due to the low magnetic energy stored in the unit volume of ferrite, the saturation magnetic induction (Bs) is also low (usually only 1/3 to 1/5 of pure iron), which limits its application in the field of low-frequency strong electricity and high power requiring higher magnetic energy density.
Typically, the ferrite can be divided into three types: permanent ferrite, soft ferrite, and microwave ferrite.
The small black magnet we usually see is usually made from permanent ferrite. Its constituent raw materials are mainly iron oxide, barium carbonate, or strontium carbonate. After being magnetized, the strength of its residual magnetic field is high, and it can maintain the residual magnetic field for a long time. Permanent ferrites have a wide application in our daily life. For example, speaker magnets are usually made of permanent ferrite.
Soft ferrite is prepared by sintering ferric oxide and one or several other metal oxides (for example, nickel oxide, zinc oxide, manganese oxide, magnesium oxide, barium oxide, strontium oxide, etc.). The reason why it is called soft ferrite is that when the magnetizing magnetic field disappears, the residual magnetic field is little or almost no. Soft ferrite is usually used as a choke coil or the core of an intermediate frequency transformer. This is completely different from permanent ferrite.
Microwave ferrite refers to ferrite materials with gyromagnetic properties. The gyromagnetism of magnetic materials means that under the action of two mutually perpendicular DC magnetic fields and electromagnetic wave magnetic fields, during the propagation of plane-polarized electromagnetic waves in the material in a certain direction, the polarization plane will continuously rotate around the propagation direction. Microwave ferrite has been widely used in the field of microwave communication.
Thank you for reading our article and we hope it can help you to have a better understanding of what is a ferrite. If you want to know more about ferrite, we would like to recommend you to visit Stanford Magnets for more information.
Stanford Magnets is a leading magnet supplier across the world who has been involved in R&D, manufacturing, and sales of permanent magnets since the 1990s. It provides customers with high-quality ferrite magnets at a very competitive price.