The wonderful world of magnets

If you have an interest in finding out about rare earth magnets, you may want to learn about the history of magnetism, which begins around 600 BC when the Greek philosophers commented on the magnetic properties of natural ferric ferrite stones. One of those Greek philosophers. Aristophanes, discovered electric charge, although this was thought to be unique to amber and its true potential remained a mystery for another two thousand years. Around AD 1600, the reports of Dr William Gilbert--following his investigation into the magnetism of amber--included the first recorded use of the term "electric", derived from "elektron", the Greek word for amber.

Dr Gilbert demonstrated that many substances besides amber are electric, and that there are two different electrical effects. Gilbert also solved the mystery of the workings of a compass by explaining that the compass needle points north-south because the Earth is magnetic. In 1747, Benjamin Franklin took Gilbert's theories to the next level by working out that electric charge is a result of two different types of electric forces: a force that attracts and a force that repels. As the saying goes: opposites attract.

Many different types of magnets are used today across all industrial sectors. Rare earth magnets are the strongest type of magnet available and include samarium cobalt and neodymium iron boron, which are the most common commercial alloy formations. Samarium cobalt has a strong resistance to oxidation and can cope with temperatures up to 300C. The down side of samarium cobalt is that it is brittle and therefore susceptible to chips, cracks and fractures. Neodymium iron boron has similar properties to samarium cobalt, but it is less resistant to extreme heat and is more easily oxidized. As neodymium iron boron is such a high energy magnet, they are ideal for compact styles and make lower manufacturing costs a possibility. Because it is highly corrosive, it must be treated before it can be used for certain applications.

The power and potential of rare earth type magnets means they have replaced many other types of magnets, such as alnico. Alnico is a combination of aluminum, cobalt and nickel and although they have a good resistance to heat and can be formulated in unique shapes, they are low energy products and have a low coercive force compared to their rare earth counterparts.

The cheapest and more commonly used magnets are ceramic magnets, also known as ferrite. They are made of a mixture of iron oxide and barium or strontium carbonate. The lower cost is due to the higher availability of these elements. Although they are low energy products and have a tendency to be brittle, they possess a high coercive force and are extremely resistant to corrosion.

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