****NON-TECHNICAL ABSTRACT**** Magnetism in solids is based on the fundamental property of the electron known as intrinsic magnetization or spin. The spin has a direction. When a pair of electrons forms a chemical bond their spins have different directions and cancel each other, therefore, most materials are non-magnetic. However, some multi-electron atoms, ions or molecules exhibit a substantial magnetization due to the presence of non-cancelled spins. In the case of a strong interaction (magnetic exchange) between these electrons, their spins may line up parallel at a certain temperature (Curie temperature) wherein the solid becomes a magnet. Generally, these electrons are not involved in chemical bonding. This project will pursue experiments to resolve the relationship between the magnetic interaction in organic-based magnets and the chemical bonding that holds these solids together. A deeper understanding of magnetic exchange and of means to control the Curie temperature in organic-based magnets will be an important advance towards application of organic-based solids in data storage and processing. This project will also support the education of PhD students in advanced magnetism studies and provide an excellent means by which both academia and/or our most advanced technology industries will benefit.
This project will address the relationship between the proposed magnetic exchange pathways in molecule-based magnets and the chemical bonding that holds these solids together. M[TCNE] (M = 3d transition metal, TCNE = tetracyanoethylene) organic-based magnets are an important class of solids for understanding magnetic exchange and correlations, as well as for potential applications. One-, two and three dimensional magnetic interactions can be realized by changing ligands (different from TCNE) around the transition metal, thereby enabling the magnetic exchange to be systematically modified and its interplay with chemical bonding rigorously studied. Varying the 3d orbital filling, anion size, and pressure will allow for the systematic alteration of the states that may participate in magnetic exchange due to symmetry considerations and the degree of metal-ligand orbital overlap; resulting in a change of the ordering temperature. A deeper understanding of magnetic exchange and how to control the ordering temperature in these organic-based magnets will be an important advance not only in the magnetism community but also as regards the potential application of organic-based solids as injectors of spin-polarized carriers for data storage and processing. This project will also support the education of PhD students in the electronic structure description of magnetism and advanced experimental techniques. The research provides an excellent means by which both academia and/or our most advanced technology industries will benefit.
Magnetism in solids is based on the fundamental property of the electron known as intrinsic magnetization or spin. The spin has a direction. When a pair of electrons forms a chemical bond their spins have different directions and cancel each other, therefore, most materials are non-magnetic. However, some multi-electron atoms, ions or molecules exhibit a substantial magnetization due to a presence of non-cancelled spins. In the case of strong interaction (magnetic exchange) between these electrons their spins may line up parallel at certain temperature (Curie temperature, Tc) wherein the solid becomes a magnet. Generally, these electrons are not involved in chemical bonding, although they should be close enough to make a Curie temperature practical for broad applications, in particular, data processing. This study addresses the magnetic exchange between electron spins in molecule-based magnets, and how the interaction is facilitated by chemical bonding that holds these solids together. M[TCNE] (M= 3d transition metal, TCNE = tetracyanoethylene) magnets are an important class of solids with examples of very high magnetic ordering temperature, Tc (below which the material is magnetic) in excess of 400 K, allowing for realization of some microelectronic applications. By varying the metal ion, anion size, and pressure we were able to systematically alter Tc thus allowing for a relationship between bonding and magnetic exchange to be established. A deeper understanding of magnetic exchange and how to control Tc is an important advance not only in the magnetism research but also with regard to application of molecule-based magnetic solids as injectors of spin-polarized carriers. This project also supported the education of PhD students in the advanced magnetism studies and provide an excellent means by which both academia and/or our most advanced technology industries will benefit.
