Ferrite magnets are easy to recognise due to their dark-grey colour. Unlike neodymium magnets, they don't need any coating thanks to their non-corrosive material. We carry ferrite magnets made of strontium ferrite (SrFe) in our assortment which are all axially magnetised. Ferrite magnets are also known as raw magnets, hard ferrite magnets, ceramic magnets or ceramic permanent magnets. The advantages of ferrite magnets at a glance:
- Temperature-resistant from -40 °C to 250 °C
- Rust-proof and therefore ideal for outdoor use
Characteristics of ferrite magnetsThe distinguishing feature of ferrite magnets is their characteristic black colour. Ferrite magnets are mainly known in the form of classic board magnets that can be found in schools, offices and at home. However, due to their properties, raw magnets made of ferrite are also used in industry. Ferrite magnets are ideal as raw magnets for further processing. Because, unlike neodymium magnets which permanently lose their magnetisation at 80 °C, ferrite magnets are temperature-resistant up to 250 °C. That’s why magnets made of ferrite are utilised where the emphasis is not so much on the high magnetic force of a magnet but rather on its durability. The advantage of ferrite magnets is that they last a long time under extreme conditions. They are also not susceptible to chemicals, lyes and salts. Magnets made of ferrite belong to the group of permanent magnets.
Ferrite magnets are the most widely produced type of magnet in the world. They consist mostly of ceramic materials, which is why magnets made of ferrite are also known as ceramic magnets. Since they are very inexpensive to manufacture, ceramic permanent magnets are used in products and applications that call for a low-cost permanent magnet. These include loudspeakers, microphones, toys or certain motors, pumps and magnetic filters.
What is the difference between magnetically soft ferrites and magnetically hard ferrites?There are two types of ferrite, namely magnetically soft ferrites and magnetically hard ferrites. The difference lies in the level of coercive field strength. Magnetically soft ferrites have a coercive field strength that is as low as possible, whereas the coercive field strength of magnetically hard ferrites is as high as possible. Put simply, this figure indicates how well a magnet retains its magnetisation when exposed to an opposite magnetic field. The higher the number, the better. Magnetically soft ferrites are used in electrical engineering, whereas magnetically hard ferrites are used, for example, in loudspeakers or microphones.
The manufacturing process for ferrite magnetsThe manufacture of ferrite magnets is a complex process where the materials pass through many stages. In simple terms, the manufacturing process works like this:
- The raw materials, among them iron-oxygen compounds such as iron(III) oxide or hematite, are milled into a very fine powder.
- This fine powder is heated to 1000 °C in a step called calcining, then mixed with water and a binding agent before being dried, turning the mixture back into a powder.
- Once the powder is dry, it is pressed into the shape of the raw magnet. However, at this stage, they are not yet magnetic.
- The ferrite magnets then go through a sintering process. During sintering, the particles of the pressed powder are fused together or compacted by applying heat, which densifies the magnet.
- The next step is to grind and polish the magnets.
- Finally the ferrite magnets are magnetised. Picture it like this: Every fine grain of the powder is already magnetic in itself. However, since their magnetic fields act in random directions, the magnetic field of the magnet cannot be concentrated. The goal of the magnetisation process is therefore to have the magnetic forces ultimately act in the same direction. During magnetisation, the magnetic forces of the metallic materials are brought into the so-called preferred orientation for magnetisation with the help of an external magnet. You can find detailed information about this process in our Magnetism A-Z Glossary under Magnetisation (in German). The ferrite magnets in our assortment are anisotropic. It means the magnets are magnetised in a predetermined direction. You can find more on this topic on our FAQ page Is this magnet isotropic or anisotropic?.
- The process is repeated so that the magnetisation does not dissipate.
- The ferrite magnets are now ready for further processing.