Here are some of the projects that our group is currently working on:
(1) Geometrically frustrated systems
Geometrically frustrated magnets are materials which cannot form conventional magnetically ordered ground states at low temperatures. According to the third law of thermodynamics, all systems should (in theory) attempt to find a ground state which minimizes the free energy, which tends to be a low entropy state. In the lab, we can design materials which have problems ordering at low temperatures due to the topology of the spins and the nature of the interactions between the moments. For example, spins which tend to orient antiferromagnetically at low temperatures that reside on triangles cannot order into what is called a Neel state (an up-down-up-down configuration). The system is said to be “frustrated”.
The interesting phenomena in these systems emerges when an energetic compromise takes place between the spins to form some new state of magnetism. Some of these materials are spin glasses, for example, at low temperatures in the absence of disorder. Some materials enter a so-called “spin liquid” state where the spins are fluctuating down to zero Kelvin, and only have short-ranged order interactions. Others form a “spin ice” state where the spins freeze into a configuration that, spin for spin, can be calculated based upon how protons freeze out in water ice.
Our group is involved with the elucidation of some of these problems. In particular, we are interested in the synthesis of half-integer and integer spin systems on various lattices.
This work is an ongoing collaboration with J. Gardner (NIST), B. Gaulin (McMaster) and J. Greedan (McMaster).
(2) Orbital ordering in transition metal oxides
Many materials exhibit ordering phenomena which include orbital degrees of freedom. An understanding of these materials is not only important from a theoretical perspective - it is also of vital importance to many technological devices, such as new CMR compounds used in the computing industry. Our group has become involved in the search for new compounds which exhibit orbital ordering (such as the recently discovered Mott insulator Sr2VO4) and the characterization of these materials with neutron scattering methods.
This work is an ongoing collaboration between our lab and Prof. Grosvenor at the University of Sask. We are also using the facilities at the Canadian Light Source to characterize our materials.
(3) Exotic superconductors
Over the past ten years I have become increasing involved with the chemistry of superconductivity (namely, the synthesis and characterization of unusual superconductors). High-Tc superconductivity has been an active field of condensed matter science for the last 20 years, but we have made little progress over the last decade towards our goal of designing a room temperature superconductor. The general consensus within the field is that we clearly do not have an understanding of the mechanism for how electrons form the Cooper pairs that make up the superconducting condensate.
Our group is using solid state chemistry to design new superconductors and test their properties. We are currently focusing on analogues of the osmium pyrochlore structures to investigate the intersection of magnetic frustration and superconductivity. We are also involved with active collaborations with the Luke and Uemura group (of McMaster and Columbia Universities respectively), and with groups at the National High Magnetic Field Laboratory in Tallahassee, Florida.
(1) Geometrically frustrated systems
Geometrically frustrated magnets are materials which cannot form conventional magnetically ordered ground states at low temperatures. According to the third law of thermodynamics, all systems should (in theory) attempt to find a ground state which minimizes the free energy, which tends to be a low entropy state. In the lab, we can design materials which have problems ordering at low temperatures due to the topology of the spins and the nature of the interactions between the moments. For example, spins which tend to orient antiferromagnetically at low temperatures that reside on triangles cannot order into what is called a Neel state (an up-down-up-down configuration). The system is said to be “frustrated”.
The interesting phenomena in these systems emerges when an energetic compromise takes place between the spins to form some new state of magnetism. Some of these materials are spin glasses, for example, at low temperatures in the absence of disorder. Some materials enter a so-called “spin liquid” state where the spins are fluctuating down to zero Kelvin, and only have short-ranged order interactions. Others form a “spin ice” state where the spins freeze into a configuration that, spin for spin, can be calculated based upon how protons freeze out in water ice.
Our group is involved with the elucidation of some of these problems. In particular, we are interested in the synthesis of half-integer and integer spin systems on various lattices.
This work is an ongoing collaboration with J. Gardner (NIST), B. Gaulin (McMaster) and J. Greedan (McMaster).
(2) Orbital ordering in transition metal oxides
Many materials exhibit ordering phenomena which include orbital degrees of freedom. An understanding of these materials is not only important from a theoretical perspective - it is also of vital importance to many technological devices, such as new CMR compounds used in the computing industry. Our group has become involved in the search for new compounds which exhibit orbital ordering (such as the recently discovered Mott insulator Sr2VO4) and the characterization of these materials with neutron scattering methods.
This work is an ongoing collaboration between our lab and Prof. Grosvenor at the University of Sask. We are also using the facilities at the Canadian Light Source to characterize our materials.
(3) Exotic superconductors
Over the past ten years I have become increasing involved with the chemistry of superconductivity (namely, the synthesis and characterization of unusual superconductors). High-Tc superconductivity has been an active field of condensed matter science for the last 20 years, but we have made little progress over the last decade towards our goal of designing a room temperature superconductor. The general consensus within the field is that we clearly do not have an understanding of the mechanism for how electrons form the Cooper pairs that make up the superconducting condensate.
Our group is using solid state chemistry to design new superconductors and test their properties. We are currently focusing on analogues of the osmium pyrochlore structures to investigate the intersection of magnetic frustration and superconductivity. We are also involved with active collaborations with the Luke and Uemura group (of McMaster and Columbia Universities respectively), and with groups at the National High Magnetic Field Laboratory in Tallahassee, Florida.