Silva attracted by magnetics group

Magnets form the basis of computer technology, so the speed at which magnets can act and react has become extremely important. The Nanomagnetics and Spin Dynamics (NSD) group in the School of Physics recently hosted Dr Tom Silva, from the National Institute of Standards and Technology (NIST) in Colorado, to work with them on a development of a high speed magnetometer which measures magnetisation at very short time scales.

At NIST, Dr Silva had created of a new type of magnetic experiment called the Pulsed Inductive Microwave Magnetometer (PIMM). The technique provides the most accurate measure of magnetic dynamics possible to date and has already uncovered new microscopic phenomena related to physical processes controlling microwave absorption by ferromagnets.

Data obtained with this equipment is of particular interest to the computer industry because it can measure accurately and simply the speed of magnetisation reversal, which directly relates to how quickly information can be recorded in computer hard disks. About 85 to 90 % of all digital information in the world today is stored magnetically and the industry associated with this is worth $150 to $200 billion annually in gross sales.

Dr Silva's three-month visit is part of a collaboration that began with Associate Professor Bob Stamps and the NSD group and is supported by funding from the Gledden Foundation. The group including ARC Postdoctoral fellows Dr Rob Woodward and Dr David Crew, and honours student Kim Kennewell, have been working with Dr Silva, to build the world's second PIMM at UWA.

Dr Silva explained that much of the work at the National Institute of Standards and Technology is in support of metrology, which is all about creating and maintaining standards for measurement. This work is only successful if the metrology developed at NIST is adopted by other researchers. "Rob Woodward has had some very clever ideas for developing the equipment and we have built a unique instrument here, rather than just a copy of the original," he said. "And Bob Stamps, who has a brilliant theoretical mind, has been helping me to understand some of the theoretical aspects of the measurements," Dr Silva said.

"The original reason we were interested in Tom's equipment, even though there are other methods of measuring things that happen very fast - and we're talking less than one-billionth of a second - was its simplicity," Dr Woodward said. Another advantage of the PIMM is that it can record measurements in seconds, that would previously have taken months to complete.

"This piece of equipment builds upon a fundamental property of magnets that Einstein proved in his one and only effort in experimental physics: magnetism has momentum," Dr Silva said. He explained that that momentum created a precessional force against which a magnet must fight as it reverses its magnetism. "This equipment allows us to see the precession - which is the ringing or resonance of the magnet," he said.

"The equipment will also be used to investigate several other phenomena in magnetic systems, including how small you can make pieces of information that are stored on your hard drive before they become unstable," said Dr Woodward. Kim Kennewell's honours project involves looking at high speed effects on very small magnetic particles. Dr Crew is working on understanding resonance effects in coupled magnetic materials, and received a UWA Research Grant to buy one of the world's fastest, low-noise pulse generators -- a vital component of the PIMM.