Obituary of Walter V. Weyhmann

The School of Physics and Astronomy and the Institute of Technology lost a distinguished colleague and friend this autumn when Walter Weyhmann, Emeritus Professor of Physics died on Saturday, September 24, 2005 at the age of 69. Weyhmann joined the Physics Faculty at Minnesota in 1964 after a year’s postdoctoral work at Harvard with his Ph.D. mentor, the late Francis Pipkin.

Weyhmann moved rapidly through the ranks at Minnesota, being promoted to Associate Professor in 1968 and to Full Professor in 1975. The faculty was truly impressed with his breadth of knowledge of physics and his organizational skills, and before he could be consider a senior member, he was made Acting Head of the School of Physics and Astronomy in 1973 and Head in 1975. He served in this capacity through 1982. He later served as Associate Dean and Acting Dean of the Graduate School during a time of transition.

Weyhmann’s research spanned several broad areas of experimental physics, starting with nuclear and chemical physics at Harvard, and branching out into condensed matter physics at Minnesota. Weyhmann was an expert in the technology of refrigeration and temperature measurement below 1K. He was a pioneer in the development of experimental platforms. He built one of the first dilution refrigerators equipped with a nuclear magnetic cooling stage and a SQUID measurement system, which was used for the investigation of the properties of materials at temperatures of the order of 1 mK and below. This is a very difficult regime as there are serious problems of heat transfer and temperature measurement as well as the need to isolate the experimental environment from sources of stray heating. The apparatus is complex, and there is no room for error if it is to work at all.

Weyhmann’s best-known work was his landmark discovery of nuclear magnetic ordering in the the Van Vleck paramagnet, PrCu6. This was the first example of nuclear magnetic ordering in a metal in which the complete system of conduction electrons, nuclear moments, phonons, was in thermal equilibrium. He subsequently investigated the critical behavior of this materials near its 2.5 mK magnetic ordering temperature.

Weyhmann was a master classroom teacher. He was able to get across complex ideas in a physical and understandable manner. Although a strict taskmaster, he captured the attention of his students. He was hands-on in directing the work of his graduate students. Much of the apparatus in his laboratory was designed by Weyhmann and his students, and built in the physics machine shop. For the students, this was an invaluable part of learning to be an experimental scientist.

As Head of the School of Physics and Astronomy, Walter made several invaluable contributions. He succeeded in hardening the positions of young faculty in the experimental particle physics group, paving the way for the development of the Soudan Mine research facility, which now houses one of the detectors for the Main Injector Neutrino Oscillation Search (MINOS). He was instrumental in obtaining the grant from the Northwest Area Foundation, which added about six positions to the department. These individuals became key members of the faculty.

Weyhmann was also an avid photographer. His work was technically impeccable, carried out using state-of-the art equipment, but it was also artistically of exceptionally high quality. He developed a course physics of photography, which was extremely well received by students, and which was adopted by other universities.

All of us who knew Walter will miss his honesty, forthrightness and knowledge. He made a difference in his scientific field, in the physics department, and in the university. He is survived by his wife Rose; daughter Elizabeth Freeberg, son-in law Brian Freeberg, and grandchildren, Michael, Anna, Darryl, and Peter.