报告人简介 Hao Zeng received his B.S. degree from Nanjing University and Ph.D. from University of Nebraska. He was a postdoc fellow at IBM T. J Watson Research Center between 2001 and 2004. He joined the Physics Department at the University at Buffalo, the State University of New York as an Assistant Professor in 2004, and was promoted to Associate Professor with tenure in 2009. He is the recipient of an IBM Research Division Award, National Science Foundation CAREER award and UB Exceptional Scholar Award. Dr. Zeng has published more than 60 papers in Journals including Nature, Nature Nanotechnology, Nano Letters, Journal of the American Chemical Society and Advanced Materials. These papers have been cited for more than 4,000 times. Dr. Zeng’s main research area is condensed matter and materials physics. His present research interests focus on nanoscale magnetism and spintronics, photovoltaic materials and biomagnetics.

报告摘要
Geometrical frustration refers to a phenomenon in which the geometrical properties of the crystal lattice or the presence of conflicting interactions forbid simultaneous minimization of the interaction energies acting at a given site. This results in macroscopic degenerate ground states with zero point entropy. In magnetic systems, geometrical frustration leads to exotic states such as spin ice and spin liquid. In this talk, I will briefly introduce the concept of geometrical frustration and some related interesting work in magnetic systems. I will then discuss two pieces of work we did recently, where we studied spin relaxation in rare-earth titanates using ac susceptibility: (a) an emergent spin relaxation mode in pyrochlore (DyTb)2Ti2O7, where the mother compounds Dy2Ti2O7 is a spin ice and Tb2Ti2O7 is a spin liquid; (b) a novel slow spin relaxation in monoclinic Nd2Ti2O7, where we believe the behavior originates from spin spin correlations.