Knight Shift Anomalies in High Magnetic Fields

Graduate student Abby Shockley’s work on the Knight shift anomaly in CeIrIn5 has been selected as a Editor’s Suggestion in Physical Review B.

This heavy fermion system exhibits a mysterious anomaly at 30 K, in which the microscopic susceptibility measured by the NMR Knight shift differs from the bulk susceptibility measured by SQUID magnetometry. The origin of this behavior is not well understood, and in order to learn more about this behavior, students Abby, Nick and Dave took her sample to the National High Magnetic Field Laboratory in Tallahassee, Florida.   By measuring the Knight shifts of two separate NMR-active sites in this material, they were able to probe the same information without the need for separate SQUID measurements.

They discovered that magnetic fields up to 30 Tesla do not significantly affect the onset temperature of the anomaly.  This result is surprising because naively one would expect the magnetic field would strongly affect the development of the heavy electron behavior at low temperatures.    This result provides an important new constraint on theories of heavy electron behavior.