What you need to know about Ferrite Magnets

A Ferrite magnet is a category of permanent magnet. Its major constituent is Iron (III) oxide. It is the simplest of all existing permanent magnets and therefore also lower in cost compared to them. They are also used as magnetic cores for transformers among other applications. They are hard and brittle.

A Ferrite magnet is a ceramic and also a magnet therefore it attracts ferromagnetic materials like itself, and may attract or repel other magnetic materials depending on their magnetivity. They are classified broadly into two categories depending on their magnetic properties – hard ferrites and soft ferrites.

These categorizations do not depend on the hardness or softness of the magnets but rather on their magnetic coercivity with soft corresponding to low coercivity and hard corresponding to high coercivity.  All Ferrite magnets degrade in magnetic properties linearly with temperature, that is, as the temperature is increased the strength of the magnet decreases.

The strength of Ferrite magnets is measured in Tesla. Tesla is the unit of measurement of the strength of a magnet i.e. its magnetic field and is named after the Serbian scientist Nikola Tesla.

Manufacturing Ferrite Magnets in the industry

The manufacture of Ferrite magnets is an elaborate process involving pressing, sintering, injection molding, special machining etc. Ferrite powder is first pressed and then the pressed product is heated in a sintering furnace below its melting point to form a solid magnet.

Pressing can be of two types – wet and dry. A wet pressed magnet has superior magnetic properties as compared to a dry pressed one but the latter shows higher physical tolerance. Sintering is the process that creates the solid magnet out of the pressed powder by heating the latter to a high temperature. It takes place in a specific atmosphere such as one with a shortage of oxygen.

Ferrite is brittle, and therefore can easily chip or crack. To machine this material it is imperative to use special machining techniques. While magnetizing them no special care is required other than the fact that since large blocks of Ferrite magnets are pretty strong, care should be taken to ensure that they don’t snap towards each other.

The applications of Ferrite magnets

Ferrite magnets are used in electronic inductors (in applications such as switched-mode power supply(SMPS)), transformers, electromagnets, motors, magnetic couplings, for sensing, loudspeakers, holding-magnet systems, crafts, magnetic therapy, novelties, and toys etc.

It is an important component used in magnetic tapes and in computer memories. It also finds use in electromagnetic instrument pickups because of its low cost and high output.