Researchers at Ames Laboratory have developed a method for measuring the magnetic properties of superconducting and magnetic materials that exhibit unusual quantum behavior at very low temperatures in high magnetic fields. Photo: Ames Laboratory, US Department of Energy.Measuring the properties of superconducting materials in magnetic fields at temperatures close to absolute zero is difficult, but necessary for understanding their quantum properties.
"For many modern (quantum) materials, to properly study the fine details of their quantum mechanical behavior you need to be cool. Cooler than was formerly thought possible," said Ruslan Prozorov, a physicist at the US Department of Energy's Ames Laboratory, who specializes in developing instrumentation for measuring such things.
Prozorov and his research team have developed a method to measure the magnetic properties of superconducting and magnetic materials that exhibit unusual quantum behavior at very low temperatures in high magnetic fields. They are now using the method to investigate properties such as quantum critical behavior, mechanisms of superconductivity, magnetic frustration and phase transitions in various materials, many of which were first fabricated at Ames Laboratory. They report their findings in a paper in the Review of Scientific Instruments.
Their method is based on placing a tunnel diode resonator, an instrument that makes precise radio-frequency measurements of magnetic properties, in a dilution refrigerator, a cryogenic device that is able to cool samples down to a milli-Kelvin temperature range. While this has been achieved before, previous studies did not have the ability to apply large static magnetic fields, which are crucial for studying quantum materials.
Prozorov's group worked to overcome the technical difficulties of maintaining high-resolution magnetic measurements while at the same time achieving ultra-cold temperatures down to 0.05K and magnetic fields up to 14 tesla (T). They had already used a similar circuit in a very high magnetic field (60T), in experiments conducted at the Los Alamos National Laboratory.
"When we first installed the dilution refrigerator, the joke was that my lab had the coldest temperatures in Iowa," said Prozorov, who conducts his research where Midwestern winters are no laughing matter. "But we were not doing this just for fun, to see how cold we could go. Many unusual quantum properties of materials can only be uncovered at these extremely low temperatures."
The group has already used this method to study pairing symmetry in several unconventional superconductors, map a very complex phase diagram in a system with field-induced quantum critical behavior and uncover very unusual properties of a spin-ice system. "None of which would be possible without this setup," said Prozorov.
This story is adapted from material from Ames Laboratory, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.