Getting the average person hooked on physics can pose something of a challenge. Black holes and multiple universes are an easy enough sell, but try the room temperature spin Hall effect on for size and you'll see what I mean. Mercifully, the Royal Swedish Academy of Sciences has seen fit to award this year's Nobel Prize for physics to a couple of guys who did something we can all appreciate: making it technologically feasible to cram a wall full of CDs onto a slick white gadget the size of a deck of cards and thereby revolutionizing the art of gazing blankly into somebody's armpit during the morning subway crush (at least in New York City). Albert Fert of Universite Paris-Sud in Orsay, France, and Peter Gruenberg of Germany's Forschungszentrum Juelich will split the $1.5 million prize for their independent discovery 20 years ago of an effect called giant magnetoresistance, in which the current flowing across a sandwich of thin magnetic and conducting layers varies dramatically depending on the direction of a magnetic domain placed next to it. If that sounds like a familiar concept, it's because hard drives in everything from the laptop to the Wii console Xbox 360 Hard Drive store data in precisely that form. Toggling a bit from 0 to 1 in a computer's memory is the same thing as switching the orientation of that bit's magnetic field. By finding a vastly more sensitive way to distinguish those fields, which grow weaker as bits get smaller, Fert and Gruenberg paved the way for the high-density hard drives that brought us the iPod, digital video recording and the continuing gains in laptop and desktop memory. Our Reuters story (available for a few weeks) has a good quote:
"A computer hard disk reader that uses a GMR sensor is equivalent to a jet flying at a speed of 30,000 kilometers (19,500 miles) per hour ... at a height of just one meter above the ground, and yet being able to see and catalogue every single blade of grass it passes over," [Ben Murdin, a physics professor at the University of Surrey in southeast England] said.
And sort of like a B-movie franchise, researchers keep uncovering new, more powerful forms of magnetoresistance: colossal magnetoresistance, ballistic magnetoresistance and (my personal favorite) extraordinary magnetoresistance, to name three. Mere giant magnetoresistance, which debuted in commercial hard drives back in 1998, represented the first example of so-called spintronics, or electronics based not on charge but spin, the property of an electron that makes it act like a tiny bar magnet. Physicists have started thinking that more exotic magnetic effects (like that spin Hall effect mentioned above) might allow them to build quantum computers that run on spin. This year's physics Nobel should remind us that the notion of uninterruptible technological progress embodied in Moore's law doesn't just happen by magic. It takes researchers like Fert and Gruenberg working today to keep those trends moving as each new decade rolls around. Related links: SciAm explained vertical hard drives in the August, 2006, installment of Working Knowledge (available for a fee) and looked at other efforts to push hard disk density in this 2005 profile, "Kryder's Law." Read more about the growing field of spintronics in last month's feature story, "The Diamond Age of Spintronics," and the 2002 feature, "Spintronics." In May I wrote about a way to control spin in silicon. And let's not forget the room temperature spin Hall effect.