John W. Schweitzer, Professor Emeritus, and a condensed matter physicist, died on September 28, 2023.

John was born in Covington, Kentucky. He received his BA in physics from Thomas More College in Covington, and his MS and PhD degrees from the University of Cincinnati. He joined the University of Iowa faculty in 1966 and continued in the Department of Physics and Astronomy until his retirement, becoming Professor Emeritus in 2010.

John studied the peculiar properties of atomic magnets that were surrounded by a sea of moving electrons in a metal. A magnetic atom, such as iron, when placed in a nonmagnetic metal like copper or aluminum, will modify its surroundings in ways that remain difficult to predict due to subtle quantum-mechanical effects. John’s early work, begun during his theoretical PhD study at the University of Cincinnati, focused on familiar magnetic atoms like iron, but in the 1970s the community, and John, began to explore the strange properties of rare earth magnetic atoms in these metallic alloys. Computers then, and now, are insufficient to calculate the properties of these systems and so elegant solvable toy models were invented and probed in different regimes by John and others to understand the behavior of these materials. Of special interest was the observation that very tiny numbers of these atoms could dominate the conductivity of a metal alloy, especially at low temperature. The advent of “high-temperature superconductivity” in the 1980s and 1990s focused renewed attention on these rare earth magnetic atoms, and John along with his experimental collaborator Bill Savage at the University of Iowa were studying many of these unusual superconductors. After Bill’s passing, John continued the experimental work as well. He turned his attention to the interaction between magnetic atoms. In collection these magnetic atoms tend to interfere with each other, forming a special type of magnetic glass known as a spin glass. John continued to publish studies of these materials and their behavior until his retirement. This area of research has recently become very important as the magnetic atoms in alloys studied by John and his colleagues appear to provide a significant source of noise in superconducting quantum computers.

Further inquiries about John’s work can be addressed to his colleague Professor Michael Flatté, michael-flatte@uiowa.edu.