2 p.m. - 3:15 p.m. Location: FN 2.102
Dr. Ilya Sochnikov (Stanford)
Scanning Superconducting QUantum Interference Device (SQUID) microscopy is a versatile technique that is efficiently used to study various emergent phenomena, such as interface superconductivity in complex oxides, magnetism in complex oxides, and protected normal- and super-currents in topological insulators. Following an introduction, I will focus on another intriguing phenomena of magnetic fluctuations in a so-called ‘spin-ice’ material.
Spin-ices are frustrated magnets that are predicted to host exotic magnetic excitations akin to freely diffusing electrostatic charges. We use scanning SQUID microscopy on classical spin-ice Ho2Ti2O7 to discover a magnetization landscape that fluctuates in both time and space. The temperature and frequency dependence of the magnetic fluctuations reveals a gapped distribution of activation energies of the fluctuations. In contrast to theoretical expectations, this gapped distribution indicates a finite energy barrier for spin flipping. Our experiment demonstrates that scanning SQUID microscopy will powerfully complement other techniques in studies of emergent phenomena in various classical and quantum magnets by enabling space-, time-, and energy- resolved detection of spin fluctuations.