About 500 GB of data are created around the world every second, with the total amount of data doubling every two years. Approximately 600 million hard drives were sold last year to contain this data, creating $32 billion in revenue for the industry, with all of that information stored on a disc smaller than a compact disc through the marvels of nano-magnets. But don’t expect this to continue. The laws of physics are being pushed to their limit in the quest for ever decreasing bit size. The industry is looking to fundamental research to provide a roadmap to guide the development of the next generation of magnetic hard drives. At the leading edge of this research are Profs. Martin Plumer and John Whitehead in the Department of Physics and Physical Oceanography, currently in their fourth year of a collaborative research agreement with Western Digital Corporation, near San Francisco, Calif., in a project that uses numerical simulations to study the stability of data stored with ever-smaller bits. “The driver of all this cheap storage is called areal density (AD), which is how many bits you can store on a square inch of a disc,” said Dr. Plumer. “AD has increased 100 million times over the past 50 years, and for a few years in the early 2000s, the annual growth rate in AD was 100 per cent. Today it is down to about 20 per cent. To sustain even a modest growth in AD over the next decade, manufacturers will need to bring new technologies to market in a relatively short time frame, and cheaply.” He explains that while the capacity of a typical disc drive has increased exponentially with time, its price has remained relatively constant because of the fierce competition between manufacturers. However, these price wars have taken their toll. “Fifteen years ago there were eight or so such companies in the U.S.,” he said. “Today, only arch rivals Western Digital and Seagate remain and neither company can afford to let the other take the technology lead. The blistering pace of the time-to-market for these new technologies is therefore critical to staying competitive. Keeping ahead in fundamental research is essential.” The main problem with increasing AD is that it affects the stability of the stored information and limits the increases in AD. The stability problem arises because to form a bit, all the tiny nano-magnets must be aligned in the same direction. “Unfortunately, the nano-magnets would rather align in opposite directions,” said Dr. Whitehead. “Just try holding two refrigerator magnets next to each other the wrong way. Fluctuations of the nano-magnets due to thermal agitation can cause random flips that degrade the bit pattern. Even at room temperature there is enough thermal energy to potentially flip a nano-magnet in a bit. “Over time, more and more nano-magnets flip their direction and the stored information is non-recoverable. For higher AD, you need smaller bits and smaller nano-magnets, which are easier to flip — that’s called superparamagnetism. Ten years ago, hard drives had a typical warranty period of five years. Now you are lucky to get a commitment that your thesis — or photos, or music — stored on your hard drive will still be there three years later, and it’s all because of superparamagnetism.” The researchers’ computer simulations relate the stability of the nano-magnets in a bit pattern to the basic material properties of the thin magnetic films that make up a hard disc. Together with their postdoctoral scholar, Dr. Tim Fal, their part-time research assistant and PhD student Jason Mercer and Dr. Johannes van Ek, their principal collaborator at Western Digital, the professors solve time-dependent equations for interacting nano-magnets or “micromagnetics” that include the effects of thermal fluctuations. “This is not an easy problem and we need the full power of the hundreds of processors available from the Atlantic Computational Excellence Network to get meaningful results,” said Dr. Plumer. “Both Western Digital and Seagate recognize the importance of fundamental research and of funding university collaborations. Our collaborative research agreement with Western Digital supports the development of numerical models that can be used to guide targeted research in materials science to sustain the continued increase in AD over the next decade. It has also brought over US$180,000 into the local economy by providing salaries for post-doctoral scholars and students.” Dr. Plumer adds the collaboration has been a lot of fun. “We get to do the type of research that we love with the added benefit that industry is interested enough to help pay for it,” he said. “It is also a way for our students and post-docs to get exposure to real-world problems and to see first-hand how fundamental science makes an impact. They get to present their results at applied magnetism conferences, interact with industry researchers, and also visit the research and manufacturing sites of Western Digital. In fact, the training in our group has even led to one of our former post-docs landing a permanent position at Seagate in Minneapolis.”
Showcase Tag: Materials Science
Fixing Everything from Bones to Airplanes
You could call Tsanka Todorova a fixer — and her toolbox is made up of chemistry and computers. In the recent past, the Bulgarian native, who is now a research associate at Dalhousie University in Halifax, has worked to develop alloys for the aerospace industry and she’s now working on a material known as bio-glass that can be used in orthopaedics and dentistry. The latter is a kind of synthetic glass-based cement that can be used in various ways — even to repair a bone fracture.
“This project is so amazing,” said an enthusiastic Todorova. “It involves different types of materials. One of them is a type of glass used in dental materials and we are now looking to see how to make those materials for orthopaedic applications. There are different possibilities. We can use it for bone repair in the body.”
Josef Zwanziger, Dalhousie professor, Canada Research Chair in Nuclear Magnetic Resonance Studies of Materials and Todorova’s research adviser, explained that often, this material can be used in a situation where you want some dissolution of the putty.
“You might load it with antibiotics and then pack it into a fracture so that as the fracture heals itself, the additive will disintegrate into the body and will release the antibiotics as it goes,” said Zwanziger said. “That part of Tsanka’s work is done in collaboration with an experimental colleague in the Applied Oral Sciences department. On the chemistry side of things, we’re interested in the simulation aspect — in simulating the process of how water makes this glass dissolve.”
Todorova said her long-term goal within this research project is to demonstrate and develop the ways in which one would use bioactive ionomer (used in dental cement) glasses as restorative materials.
“The work would build on recent advancements in the area of synthesis and biomedical engineering,” she said. “But it would also enable o molecular dynamics to deliver non-toxic and mechanically stable ionomer glasses for biomedical applications.”
Todorova’s alloy work was all done computationally, by studying models of, for example, aluminum doped with elements such as zirconium or scandium and then computing the mechanical properties of that material and what the effect of defects would be. So-called “stacking fault” defects are inevitable in any material and can affect the alloy’s performance.
“The crystal is made up of plains of atoms that repeat over and over again, but they have to be offset from each other the right amount and if they’re not, you get a stacking fault,” Zwanziger said. “So you just basically build up the layers with an error that repeats. That’s normal. In fact, thermodynamics almost requires that to happen, but it will determine what the real performance of the material is like, so it’s important to include that in models of the materials.”
Todorova has a PhD in theoretical chemistry from the University of Sheffield, UK, a master’s in computational chemistry and a bachelor’s in chemistry from Sofia University in Bulgaria.
Compute Canada has been invaluable for her work as she uses its high-powered computing resources to run molecular dynamic simulations.
“This kind of computation requires a lot of memory,” Todorova said. “We want to understand the exact atomic structure of those materials. I am a quantum chemist so I do modelling of different materials and I use the principles of quantum chemistry and solid state physics. In general, I work on theory.”
Asked what it’s like to be a woman in science, she admitted she’s the only woman in her lab, but said she has no problem with any of her colleagues.
“I have a lot of freedom,” she said. “We have a great team, we support each other and, ultimately, we have the same goals. ”
Zwanziger said their field — chemistry — is closer to gender parity than a lot of areas in the sciences. “She’s fascinated by the computer approach to modelling. That’s an aspect that she really enjoys. She’s very productive and she works really hard at it.”
Designing New Molecules
Jason Masuda has something in common with the alchemists of old. But instead of trying to turn lead into gold, he’s building substances that have never been seen on Earth before. Masuda is a chemistry professor at Saint Mary’s University who is building new molecules from atoms. He says the idea is to use new combinations of atoms to make an actual physical compound with unique chemical properties. “In organic chemistry there are a number of functional groups – specific groups of atoms within molecules that have very characteristic properties, such as aldehydes, ketones, and alcohols – but what we’re doing is making functional groups that have not been made before. Organic chemists understand how the normal functional groups react. We make a new arrangement of atoms and then we study them and how they react with other molecules. That gives us insights into their reactivity. That’s what chemistry is about. Reactions.” The majority of Masuda’s work is done in the lab using glove boxes in an inert environment because many of the molecules he creates are reactive to water and air. “The compounds that we make are not transient things,” he says. “They are actually something you can physically store in a lab.” Once a new molecule has been created, Masuda studies it and catalogs its properties in a library of molecules. “We purify these molecules, we crystallize them and then we analyze them using a variety of techniques. One of the key methods is by using an Xray defractometer on single crystals. That lets us see the places of the atoms in three dimensions.” Masuda also uses ACENET to conduct electronic structure calculations using software called Gaussian09 – a program that places groups of atoms into a structure that is the most stable configuration.“We use that alongside our experimental work to predict the reactivity of these molecules,” he says. Masuda will often use Gaussian to see ahead of time if a molecule will be stable enough to exist in nature. “Gaussian09 is a great tool to save us from wasting time. Because we’re pushing the boundaries of what nature allows, quite often I will generate a molecule and get it to optimize on ACENET and then, if it looks promising, we’ll make it in the lab. There’s a saying that two hours in the library saves you two months in the lab. It’s the same with ACENET. Sometimes a couple of hours with Gaussian09 will save you weeks or months in the lab.” While Masuda creates molecules in the name of pure science, he says giving scientists such as cancer researchers a palette of molecules to work with will ultimately have many practical applications as well. “Basic science leads to new discoveries,” he says. “Often we have no idea what those discoveries will be ahead of time.”