University of Texas at Austin

Tuesday, January 11, 2011

DIY: Building your own spin zone

Physics Professor Alex de Lozanne and his lab are building a $438,000 scanning tunneling microscope from the ground up.

Physics Professor Alex de Lozanne and his lab are building a $438,000 scanning tunneling microscope from the ground up.

When Professor Alex de Lozanne was a boy he made things with Tinker Toys, went on to a mechanical version of Tinker Toys and just kept on tinkering.

Even as a physicist at The University of Texas at Austin, he’s built instruments used in his laboratory.

For his latest project, de Lozanne and members of his lab are building a spin-polarized scanning tunneling microscope (STM) from scratch.

Take 60-second video tour of the microscope with Prof. de Lozanne.

With it, researchers will not only be able to see individual atoms, but also the atoms’ magnetic spin. The instrument has a magnification of one billion and a special tip that picks up the magnetic spin of the material being studied.

The microscope will be one of a handful in the world with such capabilities.

The research the instrument’s users will conduct is basic science, but what they learn could have applications down the road in computers, information storage and other fields.

De Lozanne and several other University of Texas at Austin researchers received a $438,000 grant from the National Science Foundation through the American Recovery and Reinvestment Act of 2009 to build the microscope.

The project is beyond what would be considered tinkering, but it has the feel of something happening at a garage workbench.

De Lozanne is not someone who lightly decides a piece of equipment has outlived its usefulness. Shelves around the lab are stocked with a variety of parts (some of them picked up at surplus auctions at agencies such as NASA). He even rustled up three weighty pink granite columns that had been around the Physics Department for decades. He’s using them to support the microscope’s chamber.

de Lozanne found three granite columns to support the microscope as he and his team build it.

de Lozanne found three granite columns to support the microscope as he and his team build it.

The microscope team uses off-the-shelf parts when it can and has other parts custom made by the Physics machine shop.

The instrument will have two STMs. One will operate at room temperature and it will allow the user to test the tip to make sure that it is sensitive to the spin properties of a calibration sample.

Then the tip will be moved into the STM chamber where the scanning will take place. It will operate at 4 degrees Kelvin, 452 degrees below zero Fahrenheit, and with magnetic fields up to 8 Tesla.

The two-STM setup will allow the instrument’s users to test the tip in the room temperature STM before loading them into the colder STM.

In a research paper published in Nature Materials in 2008, de Lozanne called the scanning tunneling microscope a “delicate yet powerful instrument.”

The new instrument will be even more so with the addition of a mechanism the team invented for positioning the tip as close as possible to the sample being examined.

The new mechanism works with a relay system that moves six points of support that can work independently of each other. That allows more control than a previous mechanism, de Lozanne said.

“It can stop the tip less than one nanometer from the sample,” he said.

The other researchers who applied for the grant were John Goodenough, Department of Mechanical Engineering, and Allan MacDonald, Chih-Kang Shih and Maxim Tsoi, Department of Physics.

Tsoi said the new microscope will present great opportunities for research.

“For me particularly, because pretty much all of my research is related to magnetism,” he said.

His interest is the phenomenon of spin transfer torque. That refers to a novel method to control magnetic spins with an electric current.

The team started the project in the summer and expects to finish in early 2011.

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