A hard drive surface as viewed using an electron microscope. Memory is stored magnetically in the pattern of dark and light patches.Image from Wikimedia Commons. / CC Attribution-Share Alike 3.0 Unported

The Spanish filmmaker Luis Buñuel once wrote, “You have to begin to lose your memory, if only in bits and pieces, to realize that memory is what makes our lives. Life without memory is no life at all.” The same might be said (albeit with less existential fanfare) of memory in the world of computers.

In the form of bigger hard drives, computer memory has revolutionized our ability to store everything from research articles, to Hollywood films, to cookbooks. Historically these devices have been enabled through the clever manipulation of magnetism. However, recent advances at UC Berkeley and elsewhere in the development of exciting materials known as multiferroics may be changing that recipe for success.

The inside of a modern hard drive works by almost exactly the same principles that kitchen magnets exploit when holding a wedding invitation to your fridge. A material with such magnetic (or more technically, ferromagnetic) properties such as a kitchen magnet is extremely useful because of its directionality. If you place two magnets together head-to-tail they attract, whereas if you flip the top magnet and repeat the process they push each other apart. A computer essentially writes and reads information by flipping little magnetic patches up or down and measuring what happens to another magnet placed on top of them.

There is a major difference, however, between the individual size of a magnet on your hard drive and a kitchen magnet. Each computerized bit on a hard drive may be 10 billion times smaller than the size of your thumbnail in area (see the figure above). It is precisely the smallness of these details that enable a computer to remember so much information.

In recent years, however, scientists have been playing around with more exotic forms of data storage. It turns out that some very specialized materials are not only like to be magnetically ordered, but are also naturally charged. That is to say, one side of the material likes to accumulate more electrons than the other side. Charging is a common enough effect in nature. When you rub a balloon against your hair you pull electrons from your hair onto the balloon. The subsequent tingling effect is a direct result of this charging. Thunderclouds exhibit charging when they accumulate massive amounts of electrons at their bases. When the energy is finally released it can result in spectacular shows of lightning.

When charging occurs naturally in a material, scientists say that the material is ferroelectric. A material that is both ferroelectric and ferromagnetic (or in cases, a variation called antiferromagnetic) is said to be multiferroic. If properly exploited, these extra properties may be quite useful in technology.

An experiment published last Sunday in the Nature Materials by researchers at UC Berkeley showed that electric voltages applied to the multiferroic bismuth ferrite could be used to directly manipulate a nearby material’s magnetic properties.

Stephen Wu, the paper’s lead author, explained that this could be an incredible step forward for technology. While people have been able to control magnetism using electricity before, never have they been able to do it in a way that requires no power, and never before have they been able to switch the direction of this magnetism so quickly. Such a development both saves energy and battery life, but also reduces the amount of heat within a system, thereby making it scalable. “You can make a lot of it, it’s static, and you can do it really fast,” said Wu, elaborating that if you could get such a system to work at room temperature, this magic combination of features could revolutionize the computing industry. In some of the most imaginative visions of the future, computers may not even be based on semiconductors or silicon at all, but rather on these new multiferroics and related compounds.

Silicon Valley may need to consider a name change.

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Iron filings reveal the pattern of a magnet's invisible force field.

That gave me a lot to work with—Sun-Earth Day usually does, but the more opportunity to create hands-on experiences for our visitors, the better, and when it comes to curious natural phenomena, magnetism is a fertile subject for all sorts of seemingly magical fun.

So, I turned Chabot's Chemistry/Physics classroom into a public magnetism laboratory, giving visitors a chance to learn, or relearn, some of the basics of magnets, as well as to connect the tabletop experiments to phenomena that take place on enormous scales on the Sun and the Earth.

First was magnetic polarity: playing with a set of magnets, visitors got a feel for the behavior of magnetic poles—N and S—and how opposite poles attract and like poles repel. (It's always fun to feel the pull of attraction between two magnets, but there's something extraordinary about feeling the push of repulsion—your mind just expects to see little bumpers on the magnets, but there's seemingly nothing there!)

The Earth itself is a giant magnet, as most of us know—but what many of the adults found surprising and intriguing is the polarity of Earth's magnetic field. Using small magnetic compasses, we sought out the Earth's magnetic poles: north and south. By taking careful notice of which type of magnetic pole the compass needle ends pointed to, the fact that the magnetic pole of the Earth up near the geographic north pole is a south—or 'S'—magnetic pole was revealed! This is why in physics we are often careful to refer to magnetic poles as 'S' and 'N', not south and north, to avoid confusion.

At another station, visitors made their own compasses by magnetizing an iron nail stuck through a Styrofoam packing peanut and floating it in a bowl of water. Darned if that floating nail didn't stubbornly turn to point in the same direction, no matter what direction we tried to turn it!

Station 3 was about mapping the invisible magnetic force field surrounding various magnets. Human eyes cannot see magnetic fields—but they are there and have an influence. I had constructed magnetic field mapping devices for this purpose: used CD jewel cases, with paper labeling removed, filled with a sprinkling of iron filings. When shaken gently back and forth—as if panning for gold—the iron filings align and connect in gritty little strings and conform to the pattern of the magnetic field. The strong field converging at the two poles of a magnet were boldly evident, but also to be seen were the more tenuous curls of field lines arcing through the space around the magnet.

The patterns formed by the filings were very similar to the patterns seen in images of sunspots we compared them to. On the Sun, it is not iron filings that trace the invisible magnetic fields for us to see, but hot, electrically charged gas, or plasma (mostly hydrogen and helium, but also traces of calcium, iron, and other elements). Electric charges (electrons and ionized atomic nuclei) are strongly affected by magnetic fields when they move through them. Numerous ultraviolet images of the Sun were available on computer screens around the lab for visitors to compare the magnetic patterns and shapes to.

We had more: building an electromagnet from wire, an iron nail, and a battery. This demonstrates how magnetic fields are created by moving electric charge—in the electrically conductive wire of the electromagnet, in the circulation of electrical current inside the Earth's iron core, and in the motions of plasma on the Sun. It's all moving electricity, friend.

We also conducted "Magnetic Yacht Races": pushing, via the repulsion of like poles, a floating, magnetized 'yacht' across a pond of water. The challenge of steering and propelling the yachts led to some interesting yacht designs; certain configurations of packing peanuts and iron nails proved easier to maneuver and accelerate than others.

Happy Sun Earth Day 2010! I wonder what we'll be doing next year….

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Extreme close-up of the Sun's visible surface,
showing 'bubbling' cells of convecting gas–each the size of
Northern California. credit: Hinode JAXA/NASA/PPARC

First things first: what is a solar cycle, and why is this one number 24? You've probably heard of sunspots and solar flares and disturbances in radio communications caused by solar activity, but had you noticed NOT hearing much about these things in the last two or three years?

The Sun exhibits a cyclic rise and fall in its level of magnetic activity. Being an enormous ball of roiling, circulating plasma (electrically charged gas), the Sun generates powerful magnetic fields in a way similar to how the circulating electricity in an electromagnet creates one.

Over the course of a solar cycle, the intensity and amount of magnetism generated by the Sun increases, like soup warming up on the stove, reaching a violent climax in which twisting, tangling magnetic fields break loose and release their energy in the form of solar flare explosions, coronal mass ejections, and tremendous heating of the solar atmosphere.

Sunspots are surface features formed by the presence of strong magnetic fields, and in general the number of sunspots that can be seen and counted indicate the level of magnetic activity on the Sun. For 400 years, since Galileo first started counting sunspots through his telescope, observers have kept track of sunspot counts, and over time a pattern in their number emerged. On average, the number of sunspot activity peaks every 11 years at a time called solar maximum.

I remember when I first started working at Chabot Space & Science Center, back in 1999/2000, during the last solar maximum. Using our Sunspotter telescopes on public observing days, in teacher workshops, and in my solar summer camp, we could easily count many sunspots-sometimes as many as 20 or more! Those were the days!

In the past two or three summers, however, it's a lucky week to spot just a single sunspot! Most of the time, the Sun's face has been a bland disk with few discernible surface features.

That status quo should start to change, now that we have allegedly reached solar minimum and are stepping onto the uphill slope toward the next maximum, which should happen sometime around 2011 or 2012. If you want to keep tabs on the rising solar activity, and you like lots of graphs and numbers and stuff like that, check out the Solar Cycle 24 website.

Oh, why is this Cycle 24? A 19^th Century astronomer who studied the then newly discovered sunspot cycle, Rudolf Wolf, established the cycle that spanned 1755 to 1766 as Cycle 1…and they've been counting up ever since.

But even in this "nap time" of the Sun, today's modern solar observatories and spacecraft, with their arrays of high-tech cameras and sensors, see plenty on the Sun to keep them busy.

Japan's Hinode spacecraft, launched in 2006, has returned libraries of amazing pictures and movies of solar flares, activity around sunspots, circulating hot gases, fine details of the life and times of magnetic fields…and all of this during solar minimum! I can't wait until the Sun really gets going and Hinode becomes like a camera-happy tourist in Tahiti….

Benjamin Burress is a staff astronomer at The Chabot Space & Science Center in Oakland, CA.