How can you make a magnet lose it magnetic power?

Answer 1

Methods to demagnetize a magnetThere are several ways to demagnetize a magnet: high temperature, AC magnetic fields, mechanical shocks, and physical distortion.

If we heat a magnetic material above its "Curie Temperature," its magnetism vanishes entirely. When the magnet cools down again, all the microscopic magnetic domains will point in circles, so the magnet will have zero overall field. Neodymium magnets have a low Curie Temp., so they are more sensitive to overheating than other types of magnet.

If we expose a magnet to the field from a strong electromagnet, the electromagnet will magnetize the magnet perhaps in a different polarity. But if we instead use an AC electromagnet, then move it away from the magnet, the magnet's polarity will flip back and forth, becoming weaker and weaker. The magnet will end up demagnetized. This is called "Degaussing."

Steel magnets are sensitive to mechanical shocks, and you can weaken a steel magnet by striking it with a hammer. Other magnetic materials are far less sensitive to hammering.

We can also demagnetize a magnet by forcing its poles together. For example, if we bend a horseshoe magnet so it forms a complete circle, its field will become a circle entirely inside the magnet, and it will have no poles or attraction. Or, if we grind a magnet up into small pieces, the pieces will align so the north pole of one fragment will be against the south pole of another, and the outside field will be small or zero.