A neodymium cube magnet.
Neodymium magnets are a type of permanent magnet also known as rare earth magnets, due to the fact that they contain one or more rare earth elements in the periodic table. Most are made from a metal alloy that contains neodymium, iron, and boron. They are much stronger than most magnets people are used to using, like fridge magnets. Due to the forces they generate, they can be dangerous or even fatal if not handled properly.
The term “rare earth elements” is used to describe sixteen elements on the periodic table.
These magnets are the strongest permanent magnets available and are capable, in some cases, of supporting more than 1000 times their own weight. They are manufactured in different shapes and sizes, such as cubes, discs, spheres, plates and rings, among others. Small ones are used in certain electronic devices, such as computer hard drives and headphones. They were also found useful in building engines for remote-controlled model aircraft.
The strength of neodymium magnets is indicated by the letter “N” followed by a number, ranging from N24 to N55. In theory it is possible to make one that is as strong as N64, but this remains a mostly theoretical possibility. These magnets have some strange properties when they interact with other materials due to their impressive strength-to-size ratio.
One of these properties is known as magnetic braking and can be observed by dropping a neodymium magnet into a copper tube. The magnet will fall very slowly due to the way the magnet and non-magnetic copper interact with each other. Immersing the copper tube in liquid nitrogen is said to increase this effect. A row of strong enough neodymium magnets is powerful enough to affect the speed and angle of a steel bullet in flight.
Most of the neodymium magnets in use are small and can even be dangerous if handled incorrectly. For example, if a child left alone swallows two small magnets, they can trap internal organs and cause fatal injury or infection. Even more care should be taken with larger magnets, such as those that are as big as the palm of a person’s hand. These magnets are strong enough to affect anything magnetic or electronic in a room, often with unpleasant results.
Manufacturers cannot ship these larger magnets on airplanes because they are so strong that they can interfere with an airplane’s navigation system, especially its compass. The websites of many neodymium magnet retailers are full of safety warnings about their handling. Despite these caveats, magnets can be very useful in scientific applications, both for demonstration and experimentation.