Dr. Christopher Wiebe

Dr. Wiebe is a physical chemist from the University of Winnipeg. Dr. Wiebe completed his undergrad at the University of Winnipeg in 1996, and then continued on to his Masters and PhD at McMaster University. He is a former faculty member of Florida State University and has now returned to the University of Winnipeg to continue his research. His research focuses on the synthesis and characterization of geometrically frustrated materials that cannot order conventionally, and can display interesting characteristics at low temperature, where new states of magnetism can arise. Dr. Wiebe is also interested in the study of high temperature superconductors and materials that exhibit ordering phenomena that include orbital degrees of freedom. These materials are interesting not only from a theoretical perspective but are also of importance in various technological devices.

Professor of Physical Chemistry
Department of Chemistry, University of Winnipeg
Tier II CRC in Quantum Materials Discovery
Fellow of CIFAR (Canadian Institute for Advanced Research)
Adjunct, Department of Chemistry, University of Manitoba
Adjunct, Department of Physics, McMaster University


Presentation Abstract
Splitting spins with chemistry: Moment fragmentation in frustrated magnets
The spin ice state in rare earth pyrochlores has been an object of study for decades due to the unusual residual entropy at low temperatures.   The mixture of two-in, two-out spins provides a way to observe a phenomenon known as moment fragmentation – the excitations act like magnetic monopoles.[1]   There is another way to observe moment fragmentation by investigating pyrochlores that have dipole-octopolar crystal field states such as those containing Nd3+.   Unfortunately, species such as Nd2Ti2O7 do not exist because of the mismatch between the Nd3+ and Ti4+ sites.   However, through solid state chemistry, we can create pyrochlores with mixed B-sites such as Nd2ScNbO7 (which has Sc3+ and Nb5+ instead of Ti4+).[2]   In this talk, I will introduce the idea of moment fragmentation, and then discuss how we can observe this effect in new pyrochlores that we have synthesized in the PRIME lab.
[1]    S. T. Bramwell and M. J. Gingras, Science (2001), 294, 1495-1501.
[2]    C. Mauws et al, to be submitted to Physical Review Letters (2018).