Voltage, current, resistance, resistance as a function of frequency or impedance: Did you know that electrical engineering students spend semester after grueling semester studying those properties in order to master the fundamentals of solid state physics and basic electronics? It’s true. And yet here today, the gentle readers of Daily Kos can grasp some sense of the fundamentals in just a few minutes using the electron square dance analogy.
And it should be noted that resistance and impedance are useful phenomena in electronics. For example, Edison's light bulb and your electric stove wouldn't be possible without them. But when it comes to microelectronics and especially pertaining to data storage and retreival, they're both big wet blankets. So, big question: What if we wanted to reduce the resistance/impedance to a bare minimum, so that we could really ramp up the tempo, or frequency, and cram tons more dancing and dancers into each happy prancing second and unit area of that drunk’n, swing’n barn dance?
One way would be to make sure everyone knows to spin or whirl in the same direction at the right time. It wouldn’t do, assuming we want a nice, crisp, dynamic dance formation, to have people spinning willy-nilly anyway they want! Revolving and rotating the same way would reduce stutter steps and collisions, and therefore facilitate the number of women that could move through the dance hall from one end to another in a more orderly way. And so the music could go faster, the caller could issue more instructions to the field of tightly packed dancers at a faster rate; it would reduce both resistance and impedance while allowing the caller to issue more information per unit time.
"Men swing your partner like a clock, and round right real neat, Now undock and pass them down to the beat, Ladies flow! Promenade and do-si-do the gents you do and do not know, hand-turn right way round or wrong you go!"
The propagation of electricity through various substances is about as active a field of research, with enormous, lucrative applications, as it gets. That process has been described as a watery flow, a moving electron cloud, or contained plasma. From distribution of electrical power to the quirky quantum journey through semiconductors, the humble, domesticated electron utterly dominates our modern world. But the electron doesn’t move down a copper wire or through a silicon wafer without some degree of resistance, they knock into each other and bunch up. And the faster they’re tasked to swing around an atom and move on, and the more of them trying to do it in a contained wire, the more they’re likely to impede one another, demonstrated above by lady dancers and music tempo. If we could just have a caller the electrons could hear telling them to all spin in the same direction, why then impedance would improve, and we could cram more information into the ‘dance hall’ containing the electrons. And lo and behold as it turns out, that can indeed be done: by bathing the location where the electrons are forced to flow in a magnetic field.
Sounds simple enough, apply a magnetic field to a conductor teeming with swinging, single, electrons, and they all spin in the same direction, flow improves and resistance drops. But gauging the ideal properties of that field, and developing and arranging the materials carrying the electrons to minimize resistance at a desired frequency, turns out to be a rather messy problem involving lots of intimidating math and physics. Fortunately, for the blogosphere, there are extraordinarily smart people who like nothing better than to fiddle with equations and chemical make ups and magnets, to figure it out.
Two gentlemen working independently did exactly that back in the late 80s. Because of their work, materials and tiny, precise magnets were developed which aided the flow of electrons through substances of various kinds. And that’s mighty important, because their research led to new materials and ways of arranging them which in turn gave us improved devices; some of which are probably in the PC you're reading this on.
For their efforts, this year’s Nobel Prize in Physics has been awarded to Albert Fert of the Université Paris-Sud in France and Peter Grünberg of the Forschungszentrum Jülich in Germany "for their breakthrough work in Giant Magnetoresistance. It is this discovery, made independently by each in 1988, which provided the basis for a dramatic rise in the amount of data that can now be stored on computer hard-disk drives.
Fert and Grunberg’s idea was a little more involved than our single dance hall analogy: Suppose the square dancers are all spinning the same way, and that the new ladies entering the dance are also spinning. If they spin in the same way as the square dancers, they flow right through. But if they spin the opposite way, the resistance is much bigger. So, in general, half the new ladies go through without much resistance. Now, imagine two square dances, with an empty space in between. If the two dances are spinning exactly the same way, then, as before half the new ladies go through without much resistance. But if the two dances are spinning in opposite ways, then none of the ladies get through easily—they will meet resistance in one dance or the other (See animation here courtesy of our friends at the Materials Research Science and Engineering Center on Nanostructured Interfaces at the University of Wisconsin-Madison).
Fert and Grunberg made a material with a sandwich of two magnetic materials separated by a non-magnetic material. If the magnetic fields of the two materials are in the same direction, electrons feel a low resistance and current flows easily. If they are in opposite directions, current flows very poorly. That gentle readers is a prime example of a revolutionary solid state switch, i.e. a switch with no moving parts -- outside of itty-bitty particles. Thus, by simply switching the magnetic field in one of the regions, current flow can be controlled on quantum scales. This switch allows storage of information on those minute scales. Fert and Grunberg showed that these magnetic sandwiches could be made really, really, really small.
The new hardware made with those tiny switches could store and retrieve information more quickly and on much smaller scales than previously possible. And for you, the electronic consumer with your slick laptops and palm pilots, that translated to smaller, faster hard drives and other gear to replace the clunky old fashioned ones that existed up until then. Drives and related devices were greatly shrunk in size and today this technology has enabled drives of such small dimensions that they can fit easily into sleek cell phones the size of a large cricket.
The new Nobel Laureates will split a cool one and a half million bucks in prize money alone. And, unlike more abstract (But equally fascinating) discoveries in the past that earned the prestigious Nobel Prize in Physics, the commercial payoff for this one has literally been in the billions of dollars.
So remember Fert and Grünberg the next time you fire up that laptop or iPhone1 and the electron square dance they brought to the world. Because of them, at your command zillions of enigmatic electrons extend a tiny electromagnetic handshake to each atom in your drive, are firmly, briefly gripped and are swung around its atomic partner before being conducted on down the line to promenade, with less resistance than ever before, thanks to a magnetic caller. And remember, too, science isn’t just interesting, the applications it produces aren’t simply convenient: Science pays, and it pays big.
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