Magnets are objects that generate magnetic fields. These magnetic fields allow magnets to attract certain metals from a distance without touching them. The magnetic fields of two magnets will cause them to either attract each other or repel each other, depending on how they are oriented. Some magnets occur naturally, while others are man-made. While there are many different types of magnets, two of the most popular are ceramic magnets and neodymium magnets. Each has its own advantages and disadvantages
1.Ceramic magnets(Ferrite Magnets)
A ceramic is a ferrite material made by mixing and firing large proportions of iron(III) oxide (Fe2O3, rust) blended with small proportions of one or more additional metallic elements, such as barium, manganese, nickel, and zinc. They are electrically non-conductive, meaning that they are insulators, and ferrimagnetic, meaning they can easily be magnetized or attracted to a magnet. Ferrites can be divided into two families based on their resistance to being demagnetized (magnetic coercivity).
Hard ferrites have high coercivity, so are difficult to demagnetize. They are used to make permanent magnets for applications such as refrigerator magnets, loudspeakers, and small electric motors.
Soft ferrites have low coercivity, so they easily change their magnetization and act as conductors of magnetic fields. They are used in the electronics industry to make efficient magnetic cores called ferrite cores for high-frequency inductors, transformers and antennas, and in various microwave components.
Ferrite compounds are extremely low cost, being made of mostly rusted iron (iron oxide), and have excellent corrosion resistance. They are very stable and difficult to demagnetize, and can be made with both high and low coercive forces. Yogoro Kato and Takeshi Takei of the Tokyo Institute of Technology synthesized the first ferrite compounds in 1930.
2.Neodymium magnets(rare earth magnets)
Rare-earth magnets are strong permanent magnets made from alloys of rare-earth elements. Developed in the 1970s and 1980s, rare-earth magnets are the strongest type of permanent magnets made, producing significantly stronger magnetic fields than other types such as ferrite or alnico magnets. The magnetic field typically produced by rare-earth magnets can exceed 1.4 teslas, whereas ferrite or ceramic magnets typically exhibit fields of 0.5 to 1 tesla.
There are two types: neodymium magnets and samarium–cobalt magnets. Rare-earth magnets are extremely brittle and also vulnerable to corrosion, so they are usually plated or coated to protect them from breaking, chipping, or crumbling into powder.
The development of rare-earth magnets began around 1966, when K. J. Strnat and G. Hoffer of the US Air Force Materials Laboratory discovered that an alloy of yttrium and cobalt, YCo5, had by far the largest magnetic anisotropy constant of any material then known.
3.Ceramic magnets vs Neodymium magnets
- Relative Strength of Ceramic VS Rare Earth Magnets
The strength of the magnetic field produced by a magnet is quantified with BHmax, or maximum energy product, which is measured in MegaGauss Oersted (MGOe). The higher the BHmax, the more powerful the magnet. Ceramic magnets have a BHmax of 3.5, SmCo have a BHmax of 26 and NdFeB are the most powerful of the rare-earth magnets with a BHmax of 40.
- Relative Resistance to Thermal Stress of Ceramic magnets VS Neodymium
Magnets can begin to lose strength when they are heated beyond a certain temperature, known as Tmax, and should not be operated beyond this temperature. They will, however, regain their strength when cooled below Tmax. Ceramic magnets have a Tmax of 300 degrees Celsius, as do SmCo magnets, and NdFeB magnets have a Tmax of 150 degrees Celsius. If a magnet is heated too far beyond Tmax, it will eventually become demagnetized at a temperature known as Tcurie. When a magnet is heated beyond Tcurie, it will not recover once cooled. Ceramic magnets have a Tcurie value of 460 degrees Celsius, SmCo have a Tcurie of 750, and NdFeB have a Tcurie of 310 degrees.
- Relative Durability of Ceramic vs Rare Earth Magnets
Along with their resistance to thermal stress, magnets also vary in their resistance to other stresses. NdFeB magnets are brittle and difficult to machine. They also corrode easily. SmCo magnets are slightly less brittle and are also difficult to machine, but have a high resistance to corrosion. SmCo magnets are also the most expensive type of magnet. Ceramic magnets are less costly than both SmCo and NdFeB magnets and have good resistance to demagnetization and corrosion.
- Common applications of Ceramic vs Rare Earth Magnets
Common applications of rare-earth magnets include:
computer hard disk drives,wind turbine generators,speakers / headphones,bicycle dynamos,MRI scanners,fishing reel brakes,permanent magnet motors in cordless tools,high-performance AC servo motors,traction motors and integrated starter-generators in hybrid and electric vehicles
Common applications of Ferrite include:
electronic inductors,transformers,electromagnets high electrical resistance of the ferrite leads to very low eddy current losses. They are commonly seen as a lump in a computer cable, called a ferrite bead, which helps to prevent high frequency electrical noise (radio frequency interference) from exiting or entering the equipment.
- Benefits of Each
Ceramic and neodymium magnets each have different benefits. Ceramic magnets are easy to magnetize. They are very resistant to corrosion and generally do not need extra coatings for corrosion protection. They are resistant to demagnetization by outside fields. They are stronger than natural magnets, though many other types of magnet are stronger than them. They are relatively inexpensive. Neodymium magnets are the most powerful of all permanent magnets. A neodymium magnet can lift more than any other type of magnet of the same size. They are extremely resistant to demagnetization by external magnetic fields.
- Drawbacks of Each
Ceramic and neodymium magnets have different drawbacks as well. Ceramic magnets are extremely brittle and easily broken. They cannot be used in machinery that experiences a lot of stress or flexing. They become demagnetized if they are exposed to high temperatures (above 480 degrees Fahrenheit.) They have only a moderate magnetic strength, making them unsuitable for applications requiring powerful magnetic fields. Neodymium magnets are relatively more expensive than ceramic magnets. They rust very easily, and extra steps must be taken to protect them from corrosion. Neodymium magnets are also very brittle and will crack under stress. They lose their magnetism if exposed to temperatures above 175 to 480 degrees Fahrenheit (depending on the exact alloy used).