Magnetic storage - why no multilevel like DVD technology?

[MadRat]

It makes sense that if DVD technology uses electromagnetic technology to store information into multiple levels of a DVD then the same principles should work for magnetic storage, too. Do they do it already or is there a technical hurdle here?

 

[Mday]

hey madrat, been a while since i saw one of your posts..

anyway

there is a slight problem. DVD technology is still an optical technology. you can get around layers through the use of different diffraction properties for optical technology. this diffraction thing is what is going to be implemented should future optical technologies take form.

magnetic storage... those use OPAQUE magnetic bits which are affected by magnetic fields. you cant have layers at all, because otherwise, you'd get interference from magnetic fields\resonance and all that good stuff.

it's like having a sheet of paper. you cant have multilayered paper, cuz you cant see through paper. if you used tracing paper, the words would overlap giving you nothing.

 

[KenGr]

Another way to look at it is that DVD writers are only one layer. As I understand it, the commercial multilayer DVD's are pressed with prewritten layers since burning a second layer would damage the first layer.

 

[TerryMathews]

It would be impossible (Well, at least nearly improbable) to support multi-layer DVD-Rs. -RWs might be possible if they are phase-change...

Basically, the layer closest to the laser is opaque at one wavelength and transparent at another, allowing the laser to read through to the inner layer.

 

[MadRat]

If I understand magnetism right then the principle of oscillation among the electrons can be focused just as you can focus light to make specific colors. In this way it should be possible to make magnetic layers of differing oscillations that would be similar to the way multiple levels of a DVD use different light frequencies to denote on and off levels. More importantly the light is focused by multiple lasers on a DVD to bounce off specific depths of the DVD surface, just as its possible to tilt the read heads to detect the level of energy on an angle and multiple heads would be able to triangulate specific data at variable depths of a specific x,y coordinate just as an MRI can pinpoint tumors in a body.

The technology is already there. I just wonder why its not used. Perhaps it is as simple as the reason somebody said why DVDRs are single layer, maybe its not possible to write to lower layers without disrupting the upper layers.

 

[Mday]

Originally posted by: MadRat
If I understand magnetism right then the principle of oscillation among the electrons can be focused just as you can focus light to make specific colors. In this way it should be possible to make magnetic layers of differing oscillations that would be similar to the way multiple levels of a DVD use different light frequencies to denote on and off levels. More importantly the light is focused by multiple lasers on a DVD to bounce off specific depths of the DVD surface, just as its possible to tilt the read heads to detect the level of energy on an angle and multiple heads would be able to triangulate specific data at variable depths of a specific x,y coordinate just as an MRI can pinpoint tumors in a body.

The technology is already there. I just wonder why its not used. Perhaps it is as simple as the reason somebody said why DVDRs are single layer, maybe its not possible to write to lower layers without disrupting the upper layers.

thing is, magnetic fields dont end abruptly, they drop off at 1/r^2 and this is not a good thing if you want to pact things CLOSE. thus domains which overlap are NOT GOOD. the ability to read and the ability to write are vastly different things. now i am saying that writing to multi layers is just not possible (without screwing up other layers). i am also saying reading things will also not be possible, without being stupid. you can space things apart enough to have multi layers, magnetically. but you are just better off with one layer which have bits packed closer\smaller.

 

[MadRat]

If what I heard was the way lasers get over the multilayer problem is correct, its by teaming four to seven (or more) lasers at the point of reference. A few lasers will not be strong enough to activate the DVD layer. Upon the moment the critical number reach the surface enough energy is present to create the switch.

So the only way to translate this into magnetism is if you can create a threshold within the material so that it can be selectively activated, which it sounds like is not yet possible. Hmmm, maybe buckyball technology will enable this capability if buckyballs truly happen to be resistant to magnetic waves. Or maybe, even easier to manufacturer, would be the ability to just paint layers upon plastic disks and stack them...