Geometrically Frustrated Magnetism: Not So Frustrating, After All

Dr. Benjamin Frandsen
Department of Physics and Astronomy
Brigham Young University

In geometrically frustrated magnets, the positions of the magnetic moments within the crystal lattice prevent the simultaneous satisfaction of competing magnetic interactions. As a result, magnetic ordering is suppressed and a variety of exotic phenomena may ensue, such as macroscopic ground-state degeneracy, extreme sensitivity to perturbations, and the formation of a quantum spin liquid. Experimental studies of the magnetic correlations in frustrated magnets have historically been very challenging due to the lack of long-range magnetic order, limiting our ability to understand the consequences of geometrical frustration. Here, I will introduce magnetic pair distribution function (mPDF) analysis, a new method of analyzing neutron scattering data that we have developed to study short-range magnetic correlations. I will then give two examples of the successful application of the mPDF technique to geometrically frustrated magnets. First, I will discuss our work on a new family of pyrochlore-type magnets based on transition metal fluorides, demonstrating how mPDF analysis can reveal hidden short-range magnetic correlations not accessible through conventional methods. Second, I will showcase the utility of combined atomic and magnetic pair distribution function analysis by unraveling the nature of the unusual magnetic transition in the frustrated magnet NaMnO2. Together, these examples teach us that geometrically frustrated magnets need not be so frustrating after all, as long as we use the right tools.