Does the magnetic field produced by a magnet deteriorate over time or use?
When copper is exposed to oxygen, it turns into cupric oxide which is not a very good conductor. So yes, Corrosion. On the other hand, iron has a higher electrical resistivity than copper.
copper reacts a lot more quickly when exposed to the oxygen than iron.it's the chemistry between copper and oxygen.
The magnetic field itself comes about because of the properties of the atoms in the magnet. The magnet itself may change, which of course then affects the field that it produces, but the fields themselves are just an effect, not things in and of themselves.
The short answer is no, it doesn't. The long answer is that under certain conditions it may. A permanent magnet consists of small sections called domain. In each domain, the magnetic moments of atoms are oriented in the same direction, thus strengthening each other (or rather, not canceling out). By the way, you can make a magnet out of an ordinary poker for instance if you put it into a magnetic field, like the Earth's, parallel to the force lines and hit it. This will shake up the domains and cause them to orient along the magnetic field, thus taking a non-random orientation. When a piece of material is a magnet, some of the domains are also oriented in the same direction, thus the total magnet moment across the object doesn't cancel out and you have a magnet. Now if you hit a magnet hard, you may shake up the domains and cause them to be randomly oriented thus canceling each other out. Also, if you heat a magnet above a certain temperature, the thermal motion of its atoms will also cause random orientation of the magnet moment and cancel the magnetism.
Depending on the magnet material, the shape of the magnet, how it is stored and what temperature it is exposed to, yes, degradation occurs in various degrees. High quality magnets, such as samarium-cobalt and neodymium-iron-boron magnets, have very high coercivity, meaning that it normally takes a lot to demagnetize them. But, given appropriate conditions, even high coercivity magnets can spontaneously lose some of their strength. If the magnets are stored properly - notably if there is a good magnetic path between the poles of the magnet - then the strength of the magnet can remain very close to its original strength for a very long period of time.
