As many industries become more electrified and the production of electric motors increases, permanent magnets continue to become more of an in-demand commodity.
The strongest permanent magnets are rare earth magnets, and these typically come in the form of neodymium or samarium cobalt. They contain a very strong magnetic field and are sometimes referred to as having a permanent magnetic field. They are often used in applications where permanence is favoured.
Depending on the application's budget and power requirements, the appropriate magnet type will be sourced and used.
Neodymium magnets are comprised of rare earth alloys; the major components being neodymium (NdFeB), along with iron and boron. Samarium cobalt (SmCo) magnets are primarily made from an alloy of samarium, cobalt, and in some alloys, iron.
Ferrite magnets (or 'regular' magnets) are commonly used for everyday purposes and are made of ceramic materials that have ferromagnetic properties. This type of magnet consists mainly of iron (III) oxide.
Now we know what each magnet's metal composition is, we will look at some of the key differences between these two types of magnets.
A rare earth or neodymium magnet is the most powerful of any permanent magnets and is around 2-7 times stronger than a regular or ferrite magnet. It can lift more than any other type of magnet of the same size. A rare earth magnet will generate a much stronger magnetic field output and is also generally harder to demagnetize. This type of magnet will also be more expensive than any other type of magnet, due to the rare earth elements that form its make up.
Rare earth magnets have high coercivity - meaning they are resistant to demagnetization; they are a maximum energy product and have high remanence (ability to keep magnetization strength). Samarium cobalt magnets are also highly resistant to demagnetization and corrosion.
Neodymium magnets can be prone to rust and/or corrosion. To combat this, many are covered with stainless steel coatings, which do not affect their magnetic field. The Curie temperature (the temperature at which a magnet gets demagnetized) is lower than that of a ferrite magnet.
With a good size to strength ratio, rare earth magnets can be good for applications with space or weight constraints. Apart from electric motors and generators, there are endless uses for these magnets, including magnetic separators, lifting machinery, bearings, audio equipment, and many more.
While there are great benefits of neodymium magnets, there are also some drawbacks. As mentioned above, cost will invariably be higher, they are prone to rust/corrosion and can crack under stress due to their brittle form. These magnets are also not suitable for applications that run extremely hot, as they can lose magnetism in temperatures above 480° Fahrenheit (248° Celsius).
Ferrite magnets are easy to magnetize and resistant to demagnetization by outside fields. More of a low energy product, their magnetic force is comparatively weaker than rare earth, as is their remanence and coercive force.
They are resistant to corrosion and therefore do not require coatings to stop corrosion occurring.
Ferrite magnets are often used in many everyday applications where more powerful (and expensive) rare earth magnets are not required. Other than in motors or generators, examples of uses include medical instruments, brakes, clamps and sweeper magnets.
Drawbacks of ferrite magnets include; brittle form that may break much more easily than a rare earth magnet, so they are not suitable for many applications that cause them a lot of stress. Because they have a lower magnetic strength, they can be unsuitable for many applications, and they can lose coercivity if exposed to temperatures above 480° Fahrenheit (248° Celsius).
The main difference between these two types of magnets is that rare earth magnets are made from rare earth alloys, and ferrite magnets are mainly composed of iron. With differences in composition, cost and magnetic field output, both rare earth and ferrite magnets are widely used in various applications. Apart from electric motors and generators, there is a huge range of uses for both types, and they are commonly found in many everyday objects.