The Story Of GMR Heads

lopati writes "The story of GMR heads, "the breakthrough that boosted the capacity of hard-drives from a few gigabytes to 100 gigabytes and more--came from chance observation, basic research and a vast, painstaking search for the right materials." Check out the helpful infographic." Background: This is a story, essentially, about how hard drives broke through some of the space limitations at the beginning of the 1990s - pretty cool background.

Comments

Reminds me of college...

[Bobartig]

One of my physics profs, Yumi Ijiri, moved to my school after doing a few years of research for NIST and IBM regarding GMR technology. Basically, noone could figure out why GMR worked, or how to systematically improve upon the concept. IBM found a neat combination of thin films created these extremely sensitive magnetic sectors, and instead of finding out why/how it works, they empirically tried some 22000 or so combinations until they progressively found better and better arrangements. After the fact, they hired Yumi to figure all the physics out, but her research was also inconclusive. It kinda scares me that there's stuff in my harddrive that IBM and NIST couldn't figure out after 4 years of research.

Re:30,000 combinations

[apsmith]

You start combining the elements of course. 100x99x98/6 is about 160,000, which is the number of different combinations of 3 elements you can have. But then you can also continually adjust their relative concentrations - A B_x C_y allowing x and y to be any number between 0 and infinity - in practice you might sample at 10 different points in x and y to get a rough idea: that's another factor of 100, so about 10 million ways to combine three elements just in terms of chemistry. Go look at alloy phase diagram books for a sample of the complexity you can get combining three metallic elements into alloys. And why stop at 3 elements? The high T_c superconductors take 4 or 5 or more to work.

But this isn't just chemistry either - the material is nonuniform, layered. Each layer can be composed of some different magnetic or non-magnetic alloy, and each layer can have a different thickness, and the number of layers is itself a variable. The combinatorial possibilities are in the billions! Obviously they narrowed it down considerably to find what they needed in just 30,000 samples - but there may be something even more spectacular out there among the billions of other possibilities, just waiting to be found.

That's what makes science these days so interesting :-) And so difficult :-(