Magneto-optical disc
Media that writes with laser heat plus a magnetic field but reads optically through the Kerr effect — nearly indestructible and big in 1990s Japan.
Writing takes two ingredients: a laser heats a spot in the magnetic layer past its Curie temperature, then a weak magnetic field sets that spot's polarity as it cools. Reading is purely optical — polarised light rotates by an amount that depends on the magnetisation (the magneto-optical Kerr effect). The pairing gives optical durability with magnetic rewritability.
The technique powered MiniDisc, the NeXT machine's 128 MB drive, and Sony and Fujitsu 3.5-inch MO cartridges (128 MB–2.3 GB) that were popular for archiving in Japan. Early discs needed a separate erase pass before writing until LIMDOW did it in one. Cheap CD-RW, DVD and eventually flash finished the format off.