Cold weather is great for enjoying hot cocoa by a fireplace, college football, and white Christmases. But what does it do to magnets and does the temperature of a magnet affect its strength?
As it turns out most magnets don’t mind the cold. In fact, some may perform better when the temperature drops. That’s because the atoms that comprise magnets vibrate more slowly and less randomly when cold. The result is a better alignment of the atoms that generates the magnetic field, boosting its strength.
It won’t be a dramatic difference, but if you’re curious you can monitor the change with a simple experiment.
First, check field strength at room temperature by dropping a neodymium bar magnet into a bowl of paper clips, and counting how many become attached. Then fill the bowl with water and put it in the freezer until the temperature of the water falls near freezing (32°F). Drop the magnet into the water and put the bowl back in the freezer for 15 minutes. Remove the bowl from the freezer just before the water freezes. Then pull the magnet from the bowl and count the number of attached paper clips. Compare this number to the number at room temperature. If you like, you can try the experiment again with dry ice that will further lower the temperature to -108°F (-78°C). (Use caution when handling dry ice and objects cooled by it).
Will the magnetic field continue to strengthen the colder it gets?
For neodymium magnets, it will not. Once you move into extremely frigid conditions (below -135°C), the field will begin to diminish. With neodymium magnets, field strength will decrease by 85-90% at the boiling point of liquid nitrogen (‑196°C). This is caused by the molecules in the magnet falling out of the good alignment seen at lesser temperature drops. However, when the temperature rises, the magnet will return to normal performance. The change in magnetic output is reversible, that is, no permanent loss of magnetic strength occurs.
We’ve used neodymium magnets as an example, but cold-temperature performance would be similar for Samarium Cobalt and for Alnico magnets. Ceramic magnets are the only magnet type where extreme cold would be cause for concern. If your ceramic magnet application entails exposure to temperatures below -60°C, it may result in a permanent (irreversible) loss of magnetic strength.
Interested in learning more? Contact us! Ask us about our white paper on Temperature Effects on Magnetic Output.
Tags: magnets and cold, temperature effects on magnets