Basically, demagnetization is a matter of randomizing the orientation of the magnetic dipole. Here's what you can do:-

• Demagnetization randomizes the orientation of magnetic dipoles.
• Demagnetization processes include heating past the Curie point, applying a strong magnetic field, applying alternating current, or hammering the metal.
• Demagnetization occurs naturally over time. The speed of the process depends on the material, the temperature, and other factors.
• While demagnetization may occur by accident, it is often performed intentionally when metal parts become magnetized or in order to destroy magnetic-encoded data.

Demagnetize a Magnet by Heating or Hammering
If you heat a magnet past the temperature called the Curie point, the energy will free the magnetic dipoles from their ordered orientation. The long-range order is destroyed and the material will have little to no magnetization. The temperature required to achieve the effect is a physical property of the particular material.
Self Demagnetization
Over time, most magnets naturally lose strength as long range ordering is reduced. Some magnets don't last very long, while natural demagnetization is an extremely slow process for others. If you store a bunch of magnets together or randomly rub magnets against each other, each will affect the other, changing the orientation of the magnetic dipoles and lessening the net magnetic field strength. A strong magnet can be used to demagnetize a weaker that has a lower coercive field.
Apply AC Current To Demagnetize a Magnet
One way to make a magnet is by applying an electrical field (electromagnet), so it makes sense you can use alternating current to remove magnetism, too. To do this, you pass AC current through a solenoid. Start with a higher current and slowly reduce it until it's zero. Alternating current rapidly switches directions, changing the orientation of the electromagnetic field. The magnetic dipoles try to orient according to the field, but since it's changing, they end up randomized. The core of the material may retain a slight magnetic field due to hysteresis.