How to demagnetize a magnet temporarily? How to demagnetize a magnet temporarily? Is it possible making a permanent magnet demagnetize for a short span of time? Or at least long time but temporarily!   
 A: I have demagnetized materials to try to eliminate magnetic fields from experiments.
I took a coil of wire and passed AC mains through it to create an oscillating magnetic field - The AC was connected through an AC transformer like the one in the picture.

slowly over time the voltage was reduced so a smaller and smaller magnetic field was used.
To remagnetize a strong magnetic field should be used - normally a coil with a DC current. 
Finally, if you have an application where you need a variable magnetic field it is normally easier to use an electromagnet than permanent ones. 
A: You should take an electromagnet that operates on some frequency (tens of Hertz) and creates enough large magnetic field to magnetise your permanent magnet. Then you switch on your electromagnet in the vicinity of the permanent magnet and go slowly back from the permanent magnet at the distance of several meters. After this the permanent magnet should be demagnetised.
The idea behind this procedure is that the electromagnet will magnetise the permanent magnet and its magnetisation will follow hysteresis loop that will became smaller and smaller when you go back from the magnet. 
A: Take a long bar magnet coil it and apply a current in the opposite direction.

