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.

37.8778 -122.243

The microscope is so big that it was hauled into the Center on a crane. It's housed in its own room, which is insulated to maintain an ideal temperature, and it's mounted on springs to isolate it from vibrations that make images blurry.

The TEAM 0.5, as the microscope is called, excels at producing clear images of atoms sitting side by side. This makes it very useful for the scientists who investigate the properties of the materials that we use to build everyday objects like computers and airplanes. In fact, the images they produce with the microscope may one day help build stronger, lighter airplanes, and smaller, faster computers.

Watch the World's Most Powerful Microscope television story online.

37.8774 -122.251

Star or Comet?

Remember the solar wind I wrote about a few weeks ago? This stream of protons does more than create comet tails and aurora, it also destroys all of those fancy electronics we work so hard to put into orbit.

The protons streaming from the sun carry a lot of energy, and they leave a lot of this energy behind as they pass through satellites and astronauts that don’t have the Earth’s atmosphere to protect them. The energy released wrecks havoc on the system, throwing electrons and atoms around like a game of ping-pong. This is one form of radiation damage.

Definitely a comet!
This radiation damage is harmless over short periods of time, much like an occasional X-ray at the dentist. However the solar wind becomes a problem for something like the Hubble Space Telescope or our proposed satellite SNAP which are exposed for many years.

To understand how a telescope degrades from exposure to radiation, let me give an extremely quick explanation of how we gather astronomical images. A telescope is very similar to a camera you buy in the store. The large mirror is equivalent to the lens on your camera. The part that suffers the most radiation damage is the Charge Coupled Device, also known as a CCD.

The CCD is essentially the same as the 8-megapixel chip in your digital camera. This serves as an electronic version of film, recording the image through the photoelectric effect rather than through a chemical reaction. If you can still remember how photography was in the days of film, I'm sure you can appreciate the relief of going digital. Astronomers realized this early on and were pioneers in the use of CCDs.

The photons from the subject of the photograph collide with electrons in the silicon of a CCD, knocking them free from their parent atom. The free electrons are then collected in a well near the site of the collision. Once the exposure is complete, charge is moved one well (or pixel) at a time toward a transistor which then reports the number of electrons found. This process is usually described through the analogy of a bucket brigade passing buckets of water from a reservoir to a fire.

When the CCD is brand new, the bucket brigade performs almost perfectly. If I want to observe a star, the image comes out crystal clear. However, after enough time in space and in the solar wind, the CCD begins to show its wear. The bucket brigade gets sloppy at work and has to contend with an increasingly difficult obstacle course, spilling a little bit of water (or electrons) during each transfer. That same star now leaves a trail of charge behind and begins to look more like a comet.

Now, if I am observing a star, I want my image to look like a star, not like a comet. Is that really too much to ask? Unfortunately, the CCD will inevitably deteriorate in space and astronomers have to find ways to predict and correct for this deterioration. This is what we spent yesterday discussing. We passed around some pretty good ideas but still have a bit of work to do before we can prove a new method for correcting the images. I just hope we it figured out before our satellite launches in 2015!

Kyle S. Dawson is engaged in post-doctorate studies of distant supernovae and development of a proposed space-based telescope at Lawrence Berkeley National Laboratory.

latitude: 37.8768, longitude: -122.251