Technical Information About Ferrite

Ferrite magnets

... are permanent magnets. 

This means: Ferromagnetic metal pieces are magnetized by a strong external magnetic field during the production process and then remain permanently magnetized. If handled properly, they will not lose their magnetic power even after decades.

... consist of strontium or barium and ferrite.

The ferrite used for ferrite magnets belongs to the group of ceramic materials. Permanent magnets made of hard ferrite consist of iron oxide and also either strontium (Sr) or barium (Ba, a heavy metal). For the magnetic properties it is irrelevant whether barium or strontium is used; most of the time it is the latter, simply because of the lower costs and better availability.

... are described using a hysteresis curve.

This magnetization curve contains information about the strength of the magnetization (remanence [Br]) as well as the required external magnetic force that leads to demagnetization (coercive field strength). However, the flux density in the entire space, i.e. the strength of the magnetic flux that flows through its surface, cannot be calculated analytically without complex finite element software. For cuboids and axially magnetized cylinders, the flux density can be approximately estimated using a formula along the magnetization axis.

... can only be heated to a limited extent.

To put it simply, magnetization means that the external magnetic field and the atomic magnetic moments located inside the workpiece are all aligned parallel in the north-south direction. This means the workpiece is magnetic. However, this common alignment is canceled again if the temperature is too high (when the critical temperature, the so-called Curie temperature) is exceeded). Ferrite magnets, however, are significantly less sensitive than neodymium magnets and can be heated up to around 250°C without the magnetic force suffering.

... can be produced isotropically or anisotropically.

This means: with or without a clear preferred direction. To put it simply, anisotropic magnets are magnetic, but without a clearly definable north and south pole (this is the case with most magnetic tapes, for example). With isotropic magnets, on the other hand, the direction of magnetization is clearly determined during magnetization, resulting in a clear preferred direction and a clearly defined north-south direction with a clear polar expression.

... are usually unmarked, the north and south poles have to be determined.

The easiest way to do this is to use a red-green “school magnet” or a compass. The following applies: equal poles repel each other. The north pole of a magnet is where it is attracted to the south pole of the test magnet.

... are manufactured using the sintering process.

This means: After incoming inspection, the raw materials are weighed, mixed, pre-sintered and ground into a fine powder with hexagonal crystals. With isotropic magnets, the primary material is then granulated and pressed. There are two processes used to produce anisotropic magnets: In the first, the raw material is first dried and then pressed in a magnetic field. In the second process, the raw material is wet-pressed under the influence of a magnetic field. This is followed by sintering, finishing work and cleaning. Finally, the surface can be processed, marked, magnetized or coated according to customer specifications.

 ... are insensitive and comparatively harmless.

In contrast to neodymium magnets, ferrite magnets do not necessarily need a coating. Ferrite permanent magnets have excellent corrosion resistance and functionality between -40°C and +250°C. They are highly chemical resistant. They are insensitive to oxidation and weather influences. They are also non-toxic and are environmentally friendly when destroyed in landfills. Even direct contact with food is considered harmless. However, the high iron content makes them susceptible to flash rust. Coatings are either made for visual reasons (e.g. red-green paintwork for school use) or to prevent discoloration or rusting, for example.

... may, but usually cannot be processed mechanically.

In principle, cutting or grinding ferrite magnets is possible. However, hard ferrite is a ceramic material and therefore processing involves a high risk of breakage and can only be carried out with the use of special diamond tools and usually under a water jet.

... can be magnetized in different grades.

The value Y indicates how strongly magnetized a ferrite magnet is, followed by a two-digit number (Y10 to Y35). The number indicates the energy density, i.e. the magnetic energy stored in the magnet: (WxH) max in MegaGaußOerstedt. The higher the number, the stronger the degree of magnetization. For two magnets with identical dimensions, the one with Y35 is stronger than the one with Y10. However, the volume of a magnet is more important than its degree of magnetization, because the first rule of thumb is: the larger the magnet, the stronger it is. Sometimes the magnetization is given as C; then the letter is followed by a one or two digit number. This is the classification in the American region. In Europe, instead of the Y, you can sometimes find the abbreviation HF, which stands for hard ferrite. However, we indicate the magnetization in the original classification of the Chinese manufacturers with Y as described.

... may have grooves, irregular edges or bumps.

This is due to the manufacturing process and is inherent to the material. Raw magnets are unpolished and unevenness or irregularities do not constitute a defect. Ferrite magnets can only be polished and made visually more 'elegant' using expensive post-processing processes. However, the usual areas of application do not justify these costs and effort. The magnetic effect is not affected in any way.

For magnetic properties watch our following data overview: