The news about British scientist Prof Stuart Parkin who won the 2014 Millennium technology prize for research that has led to a phenomenal increase in storage capacity of digital devices and announced the era of cloud computing, was not a surprise. The physicist joins past winners including the inventor of the world wide web, Sir Tim Berners-Lee, Linux creator Linus Torvalds and pioneer of dye-sensitised solar cells Michael Grätzel.
Stuart Parkin is an experimental physicist, IBM Fellow and manager of the magnetoelectronics group at the IBM Almaden Research Center in San Jose, California. His research is closely related to the work of Fert and Grunberg who identified giant magnetoresistance (GMR) in oscillatory interlayer coupling in magnetic multilayers. Parkin’s major achievement was the application of this phenomenon to create extremely sensitive devices that can detect tiny magnetic fields which enabled a more than 1000-fold increase in magnetic hard disk drive data density. The GMR phenomenon arises when thin layers of magnetic and non-magnetic materials are stacked on top of each other. In a very simple arrangement, a non-magnetic layer (likely copper) is sandwiched between two magnetic layers. These magnetic layers behave like bar magnets pointing either north or south. When a current is induced in this sandwich, electrons move through the layers. The amount of resistance they experience is different depending upon a quantum mechanical property called “spin”. Therefore the ‘spin’ can be aligned to the direction of the bar magnet or against it. Electrons with a spin in one direction will move more freely, so the flow of the current can be controlled by the relative arrangement of the bar magnets of the top and bottom layers. Parkin’s achievement was to develop a device based on such “spintronic” effects in which tiny magnetic fields from magnetised regions that store data within the disk drive can rotate the direction of magnetisation in one of the layers of the sandwich. The result is a sensor that rapidly experiences large changes in resistance as it reads the disk drive. In contrast to the expensive and difficult techniques used by Fert and Grunberg, Parkin made use of a simpler technique known as sputtering.
“I showed that you didn’t need these very exotic techniques but one could actually use a much simpler technique which was compatible with mass manufacturing,” he said. Later, Parkin showed that GMR is a more common phenomenon than initially thought, and can be seen at room temperature.
Recently, Parkin has proposed and is working on a novel storage class memory device, The Magnetic Racetrack memory, an experimental non-volatile memory device which could replace both hard disk drives and many forms of conventional solid state memory. Racetrack memory uses a spin-coherent electric current to move magnetic domains along a nanoscopic permalloy wire about 200 nm across and 100 nm thick. In general, racetrack memory is similar to the earlier bubble memory used in the 1960s and 1970s. Like bubble memory, racetrack memory uses electrical currents to “push” a magnetic pattern through a substrate. Therefore, a remarkable improvements in magnetic detection capabilities with the development of spintronic magnetoresistive-sensing materials and devices, allow the use of much smaller magnetic domains to provide higher bit densities. In production, it is expected that the wires can be scaled down to around 50 nm.
“I will celebrate the award by inviting my fiancée to the Vendôme restaurant in Schloss Bensberg, one of our favourite restaurants in Germany for very special occasions,” he said. The Watford-born physicist told the Guardian he planned to use the money which comes with his prize (about €1m ) to buy a house in Halle, Germany!
Parkin’s research interests also include organic superconductors, high-temperature superconductors, magnetic thin film structures and spintronic materials and devices for advanced sensor, memory, and logic applications. He is also a Fellow of the Royal Society, the American Physical Society, the Materials Research Society, the Institute of Physics in London, the Institute of Electrical and Electronics Engineers, the American Association for the Advancement of Science, and the Gutenberg Research College.