At least bubble memory was an actual product for a time, though it was competitive only in a few niche use cases. Racetrack memory sounds like it was never more than an idea.
A blast from the past! I was in grad school in 2014 when I learned about racetrack memory applications using magnetic skyrmions, they were pretty hot because they were considered topologically-protected spin textures and around that time the Nobel prize was/would be awarded to topological phase transitions and topological phases of matter, so the grant money was flowing, and this guy Matthias Klaui from the article was a bit of hot shit in this niche field I was in.<p>I remember at the time magnetic skyrmions could only materialize at low temperatures in materials like FeGe that had to be grown in a specific crystalline phase, B20 if memory serves. Fast forward to today and people can nucleate skyrmions at room-temperature using multilayers of more conventional materials, so at least that was some progress.<p>What never materialized was a disruptive technology, or even a technology. This racetrack memory thing was affected by the most common of magnetic domain wall defects: pinning. The so-called 'topological protection' promise never came true, skyrmions get pinned by defects just like regular domain walls and so then.... poof! I was fortunate to have found failure early on my skyrmion research and moved elsewhere, but at the time, boy was there froth everywhere about the revolution that's coming!<p>10-15 years later and this thing is still relegated to the lab. And truth be told, I still think this whole magnetic skyrmion thing is the same thing as magnetic bubble domains, it's just that we could study things in greater detail today and learned that these bubbles have chirality, but it always felt like this was more of a re-discovery or further refinement of something already known, rather than this new, hot, revolutionary thing it was hyped to be, but hey, maybe that's how you get money no?<p>I just find it fascinating how wrong the predictions were, how little of the promise/potential was actually realized, and what a waste of energy to be stressing about these things! Man, grad school was this weird reality-distortion field.