Do you know Ferrite Magnet?

The first magnets that people are exposed to are usually ferrite magnets, as they are the cheapest and most common. Children are often given toys made up of iron filings that can be moved around with this type of magnet — usually magnetite. If the magnet is placed on the filings, the resulting pattern they are pulled into reveals the shape of the magnetic field. The Earth itself produces a similar magnetic field, though trillions of times larger and about 10,000 times weaker.
Sintered  was developed since 1960s. It is manufactured from Oxide material by Powder metallurgical process. According to the difference in molding process, it can be divided into Dry Type and Wet Type ferrite magnets. According to the inner structure of the material, it can be divided into Anisotropic Ferrite Magnet and Isotropic Ferrite Magnet. It is considered a fundamental magnetic material, for it is widely used in many fields owing to its good magnetic performance and the low cost of its raw material. In various applications, it can not be replaced, although many new magnetic materials came out in recent years.
The Ferrite permanent magnet is also known as a Ceramic Magnet and even as hard ferrite magnet. The name is interchangeable but they all refer to exactly the same material type. They are known as Ceramic Magnets because they are electrically insulating. Ferrite permanent magnets exist in two forms – Strontium Ferrite magnets and Barium Ferrite Magnets. The Strontium Ferrite Magnets is the most common.
Ferrite / Ceramic permanent magnets are technically known as hard ferrite materials (when exposed to a brief external magnetic field, the material retains magnetism due to having high coercivity, Hc). They are not the same as soft ferrite materials as used in transformer cores (which do not retain magnetism after exposure to a brief magnetic field because soft ferrite materials have low coercivity). The high coercive force of Ferrite Magnets means they are classified as hard materials, like all the other permanent magnets.
Ferrites that are used in transformer or electromagnetic cores contain nickel, zinc, and/or manganese compounds. They have a low coercivity and are called soft ferrites. The low coercivity means the material’s magnetization can easily reverse direction without dissipating much energy (hysteresis losses), while the material’s high resistivity prevents eddy currents in the core, another source of energy loss. Because of their comparatively low losses at high frequencies, they are extensively used in the cores of RF transformers and inductors in applications such as switched-mode power supplies.
Ferrite magnets, also known as ferromagnetic materials, are generally classified into two categories based on their magnetic coercivity, or persistence of internal magnetism: soft ferrites and hard ferrites. These categorizations do not refer to the actual hardness of the magnets — both types are brittle ceramics — but rather their coercive force. Depending on whether a magnet is soft or hard, it may have different applications. For instance, a hard magnet might be used in a radio or a hard disk, while a soft one could be used as a transformer core or an electromagnet core.
Ferrite magnets are extremely popular due to their characteristics. Ferrite magnets are corrosion free – for long term performance they are superb; if looked after they are capable of exceeding most products lifecycles. Ferrite magnets can be used up to +250 degrees C (and in some cases up to +300 deg C). Ferrite magnets are also low cost, particularly in high volume production runs. We offer 27 grades of ferrite permanent magnet.
Edit by http://www.senmagnetics.com