Research at A221 Physics Hall

A221 Physics Hall
Iowa State University and Ames Lab - U.S. DOE
Ames, IA 50011
Tel: (515) 294-1886
Fax: (515) 294-0689

This lab is operated by Dr. Alan I Goldman of Iowa State University and Ames Lab. Currently one post-doc, Lars Lottermoser, two graduate students, Zahirul Islam, Changyong Song, and one undergraduate student, Brandon Gordon, are working here.

The main interest of our research lies in magnetic structures of ferro-, ferri-, and antiferromagnets (Zahirul and Alan) and in the high pressure studies of magnetic structures (Lars and Alan). Our research also includes density waves in solids (Changyong), and the structure of quasicrystals (Alan and Zahirul). We are also involved in the construction and instrumentation of an undulator beamline at the APS (Advance Photon Source, Argonne IL) . Most of our work is done on single crystals.

To investigate these structures, we use all kinds of x-rays, preferably from synchrotrons, and sometimes from neutrons.

The lab is equipped with three different x-ray sources:
A Mo tube source
This generator is used for a Laue-Camera and a Buerger Precession Camera. We use it almost every other day for sample characterization and alignment of singe crystal faces for polishing (precission: about 0.5°).
A Cu tube source with a high-temperature powder diffractometer.
It uses a position sensitive detector (single wire proportional counter, the brown arc in the picture) for powder x-ray diffraction at temperatures up to 800oC. This detector allows simultaneous data collection at all scattering angles between about 10 and 120 degrees.
A rotating anode source
This mighty machine (max. power: 60 kV x 300 mA = 18 kW!) is used with a 4-circle diffractometer. The generator can used with both Mo or Cu anodes. This is the most important research tool in our lab. The diffractometer is fully computerized and once the sample has been aligned by finding two independent bragg reflections, the computer can find any other reflection within no time. A closed cycle helium refrigerator can be mounted into the diffractometer so that the samples can be cooled down to 10K. A 3.6K refrigeration system is currently under construction.
Other equipment includes a diamond saw and polishing tools for sample preparation and, of course, several computers.
Current Research topics (Click here to get a list of our
recent publications ):

Magnetic x-ray scattering

The magnetic structure of RNi2B2C-Compounds (R=rare earth element):

These compounds have very interesting magnetic structures. In some of them (e.g. HoNi2B2C) magnetism coexists with superconductivity!

We use magnetic x-ray scattering (x-ray resonant exchange scattering, XRES) and neutron scattering to investigate these compounds.

If you are interested in superconductivity, take a look at the High-Tc Update, the latest news on high-Tc superconductors.

By the way, this image was created using the Persistence of Vision ray tracer .

CMXD (circular magnetic dichroism) .
A spectroscopy that can determine the local magnetic moments in ferromagnets.

Quasicrystals and quasicrystal surfaces.
How can you get perfect long range order without periodicity?!?

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