Neodymium Rare-earth magnets

Neodymium magnets are a permanent magnet made from an alloy of neodymium, iron and boron (Nd2Fe14B). The tetragonal crystalline structure gives the magnet a high resistance to being demagnetized. They were developed in 1982, by GM and Sumitomo Special Metals. Sumitomo developed the sintered neodymium magnet and eventually became part of Hitachi family of companies. There are several grades of Neodymium magnets. The grade is two numbers followed by letters. The numbers represent the magnetic strength and the letters represent the maximum operating temperatures. Most of my neodymium magnets are grade 40 and have a maximum operating temperature of 80 degrees Celsius or 176 degrees Fahrenheit. Because sintered neodymium alloy is highly susceptible to corrosion they are generally plated in nickel-copper-nickel coating for a shiny corrosion resistant finish.

I know this is all great right but whats the big deal? Well the world would not be the same with out neodymium magnets. They are heavily used in the computer industry in hard disk drives.

Neodymium desktop hard drive magnet

Neodymium desktop hard drive magnet

Advances in smaller drives that eventually went into laptops were largely made possible by neodymium magnets.

Neodymium laptop hard drive magnet

Neodymium laptop hard drive magnet

Neodymium magnets are also used in Guitar pickups, magnetic door locks, MRI’s (Magnetic resonance imaging), Cordless drill’s, wind turbines, and Motors of all sorts, even the prius has neodymium magnets in its drive motors.

They come in all shapes and sizes. Everything from small button magnets to keep cabinet doors closed to cubes, and large rods.

This small neodymium magnet has about 3 pounds of pull force.

This half inch by half inch neodymium cube has the pull force of around 24 pounds.

half inch by half inch neodymium cube

half inch by half inch neodymium cube

This larger grade N40 neodymium rod has about 28 pounds of pull force.

This is a 1

This is a 1″ by 1/2″ neodymium rod

These magnets are certainly very interesting and have a lot of uses in experiments and also in practical applications but they can also be very powerful and certainly can be dangerous. They can attract each other from several inches away and even shatter upon impact. Extreme caution should be observed. Beyond the danger that they can pose to you they can also cause damage to your electronic devices. So again caution should be observed.

For some fun drop a neodymium magnet down through a section of copper pipe. neodymium magnets will produce eddy currents when dropped down a section of pipe that will cause the magnet to tumble and slow its fall down the pipe. The best results will be if you use thick walled pipe like schedule L and a magnet that is cube shaped that has enough room to tumble.

When a the neodymium magnet falls down the length of pipe, the changing magnetic field created by the falling magnet pushes electrons in the metal tube around in a circular movement. These eddy currents have their own magnetic field which is then perpendicular to that of the magnet which therefore opposes the fall of the magnet. The magnet falls dramatically slower than it does in ordinary free fall

If you want to read more on this phenomenon you can look up Lenz’s Law

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