21 February 2012

Types of Permanent Magnets

The permanent magnets can be made from many different materials with different qualities. Each material has its strengths and weaknesses in four different categories of magnetism. These four categories are remanence, coercivity and energy products, and the Curie temperature. There are four main types of materials to make permanent magnets. What are ferrite, alnico, samarium cobalt and neodymium magnets.

Permanent ferrite magnets are made from sintered composite of iron oxide and a mixture of barium carbonate and strontium. These materials are used to create relatively low-cost magnets such as those needed to make the radio antenna. They are also very malleable. They have excellent quality in their resistance to corrosion, but are also very fragile.

Alnico permanent magnets are made when a mixture of aluminum, nickel and cobalt are sintered with iron. The magnets produced in this process strongly resist demagnetization. This gives them a higher coercivity. However, these ferrite magnets and magnets have been surpassed by the rare earth materials used to make samarium cobalt and neodymium in the late 20th century.

Samarium cobalt magnets were first developed in the 1960s and 1970s. These magnets made from rare earths, were far superior to all previous magnets designed by the industry. Some alnico magnets actually had a higher persistence or pure magnetic force, the variety of samarium cobalt. However, samarium-cobalt far surpassed previous magnetic materials in the categories of coercivity and energy products. The latter is essentially a measure of the density of a magnetic field. The Curie temperature similar, or the temperature at which a magnet is losing the magnetic properties, has led researchers to try to develop a strong neodymium magnet rare earth.

They were at first disappointed. While the magnets made from neodymium were at least equal in persistence to all substances and their previous coercivity and energy products were much higher, the Curie temperature of the magnets made from neodymium was a 400 degrees Celsius disappointing, even lower than the poorest sort of ferrite magnet. This meant that the magnet would begin to lose the qualities magnetic relatively low temperatures, which makes it pretty useless for industrial applications. Only later, when someone has discovered how to alleviate this problem by adding other rare earths such as terbium, the alloy would become desirable that these magnets in an industrial setting.

Since the development of neodymium magnets in the 1980s and 1990s, they slowly resumed the permanent magnet industry. They are increasingly used in a variety of applications. They found particular use in the most advanced technological devices currently paying factories in the form of MRI scanners, cordless tools and various appliances. The magnetic power, even in a small magnet from this substance has allowed people to use in every application.