Magnetic media and perpendicular recording in floppies

[Alex Eisenhut]

This is more of a wool-gathering question/post.

Since people have assured me that some floppy HD media can be used in a ED drive, I wonder about how it works. I didn't think it would work. Indeed most of the time it doesn't. But in some cases it does!

If a HD disk has a thicker coating could the return flux just be in the HD coating, and because the lines are spread out as they go back to the larger part of the head, it would leave the domains alone?

And if so, why did ED media have a second layer? Did it? Or is it just something I read somewhere?

And if so, why was magnetic recording longitudinal for so long? Seems even analog audio could have done this in the '60s?

Seems like a perpendicular recording head doesn't require an accurate tiny gap, but just depends on the sharpness of the point? And a sharp edge is a lot easier to make than an accurate gap. Think stick vs piston engine.

[Alex Eisenhut]

I think I found an answer. There's two types of perpendicular recording. Like, duh, I guess. Type 1 is with a soft return layer, type 2, without.

https://www.cse.psu.edu/~buu1/teaching/spring07/598d/_assoc/994BCFA15D6146A9A7C08EF5683E1A42/TheFutureOfMagneticStorage.pdf

pg 8

"(a) Longitudinal magnetic recording. (b) Type 1 perpendicular recording, using a probe head and a soft underlayer in the medium. (c) Type 2
perpendicular recording, using a ring head and no soft underlayer."

Of course now the question is why they draw a longitudinal-style head.