Could light erase a hard drive? I have been having a theoretical discussion with a colleague at work. He proposed the idea of a laser being able to erase a hard drive.
I know that a hard drive is basically a magnetic disc that can be polarised using an electromagnetic write head.
Given that light has an electrical and magnetic field component I would assume it is possible to erase or fry(electrically not thermally) electronics.
My question is this. Is it theoretically possible to erase(not destroy) a hard drive with light in the visible spectrum?
Edit: It appears I was unclear with my earlier question. In this theoretical situation, we are only interested in the effects of the electric and magnetic effects of light. Please ignore thermal effects such as heating the disc until it reaches its Curie temperature.
My personal hypothesis on the matter is that if you could get a very powerful laser that gave off light that was not absorbed by the HDD, and if all that light was in phase, that it might be possible to add up the electrical and magnetic fields to a point where the HDD could be edited(magnetically not thermally) by the light.
 A: Any erasing would likely be from thermal effects. If the light heats a spot on the disk above the material's Curie temperature, the magnetic field generated by that spot will relax. That may or may not be hot enough to destroy the disk.
You would probably want to use a short pulse from a laser focused on a small spot. This would locally heat the bit in question, and turn off before enough heat was added to raise the temperature of nearby spots.
A: The answer is NO. Gyromagnetic effects limit the rate at which magnetization can be changed.  In most situations, magnetization will not respond to frequencies much above a few GHz and certainly not to optical frequencies.  
However, all-optical switching of magnetization is a recent and active area of research (for example in 'Nature'). All-optical switching can be extremely rapid. There is some controversy over the exact mechanisms involved.  Typically these effects are observed in specialized materials and not at all in the high-coercivity, high-magnetization CoPtCr alloys used in HDDs.
A: I think your colleague may refer to the Heat-assisted magnetic recording(HAMR) driver. Basically, it is using laser as a heater but not a tool to change the electromagnetic field. For details, you may find more on Wikipedia.
