Quantum Matter Seminar

Magnetic insulators hold great promise for technologies such as spintronics and quantum information processing. These applications rely on the novel functionality of real materials, requiring a thorough understanding of magnetic ground-state properties such as ordering—whether conventional or exotic—, the corresponding low-energy spin excitations, and interactions between spin and lattice degrees of freedom. Insulating rare-earth magnets are especially suited for this purpose: strong spin–orbit coupling and crystal electric field (CEF) effects produce pronounced anisotropy and competing energy scales that can give rise to magnetic frustration.

In this talk, I will present the highly anisotropic CEF level splittings of Kramers' rare-earth ions under a magnetic field, observed via resonant torsion magnetometry and direct magneto-optical spectroscopy. This reveals unusual ground-state properties, including quadratic field-dependent Zeeman splitting and/or ground-state level crossing. I will then discuss how, in rare-earth magnets, hybridization between acoustic phonons and spin-flip excitations across the Zeeman gap produces unusual field dependence of thermal conductivity. This, in turn, offers insight into a better understanding of magnetic properties across a wide range of rare-earth magnets.