Dr. J. E. Greedan
Dept. of Chemistry
Hamilton ON Canada
Ph: (905) 525-9140
Fax: (905) 521-2773
J. E. Greedan
In our group we study the relationship between the structure and properties of inorganic solids. Our focus is on transition metal oxides (TMO's). TMO's exist in an astonishing array of crystal structures, >103 structure types are known and hundreds of new ones are discovered each year. The crystal structure and the crystal chemistry (elemental composition, bond distances, bond angles and connectivity or topology) determine the electronic structure which in turn fixes the physical and chemical properties. TMO's exhibit a rich variety of properties from electrically insulating to superconducting, transparent to highly reflecting and diamagnetic to ferromagnetic, often within the same structural family. The physical properties can be tuned by manipulation of the crystal chemistry and, in favourable cases, very minor changes in chemistry produce major changes in properties.
It is the goal of our research program to understand these structure-property relationships in detail for selected TMO systems. We synthesize new TMO's using as much of the periodic table as possible and use the excellent and extensive facilities of the Brockhouse Institute for Materials Research and the Department of Chemistry to characterize the physical properties. We also make frequent use of national and international facilities such as synchrotron light sources and neutron sources in North America and Europe.
Detailed information on current research interests is available in the Research section.
News and Updates
Congratulations Jonathan Mitchell on defending your MSc thesis!
We bid farewell to Shahab Derakhshan, who is off to fun in the sun with his new professorship at California State University, Long Beach!
|Postdoc Andrew Grosvenor leaves us for the colder, drier climes of Saskatoon as he takes his new professor position at USask. Best of luck Andelu!
The magnetoresistive "electron"-doped
(d = 0.06, 0.11) have been
investigated by neutron diffraction. While both materials
order at TN ~ 125 K, they have unique yet
related magnetic structures. The CaMnO2.94 sample
orders into a simple G-type antiferromagnetic structure, shown
on the left, which is also observed in CaMnO3.
The slightly more doped sample CaMnO2.89, on the
other hand, orders into a magnetic structure which is based
upon the G-type, but also involves a Mn3+/Mn4+
charge ordering over every four layers in the crystallographic
c direction (shown on the right). The potential of
these kinds of materials as new magnetic recording media is
great, but the mechanism for the magnetoresistive behaviour
is poorly understood. Studies such as this bring us closer
to this understanding, and demonstrate how subtle crystal
chemistry effects can result in dramatic differences in the
properties of materials. (C.R. Wiebe; J.E.
Greedan; J.S. Gardner; Z. Zeng; and M. Greenblatt Phys.
Rev. 2001 B64 )
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