This project aims at determining how geometry and magneto-optical effects are correlated in a class of Heisenberg ferromagnetic nanomaterials, rare earth chalcogenide nanocrystals. Monodisperse nanocrystal of EuS, EuO and EuTe with sizes ranging between less than 2.0 nm (quantum-confined) to about 20 nm (nanocrystals) will be produced using a thermolysis procedure of single source precursor under nitrogen atmosphere. Magnetic and magneto-optical properties of the nanocrystals will be studied as functions of crystal size, crystal boundary characteristics and local atomic separation within the crystals themselves. The studies will be carried out by means of magnetic, optical and x-ray diffraction, techniques. The different tasks and project activities are designed with the goals to encourage the participation of underrepresented groups in science, contribute to science infrastructure and integrate science and education. Educational/research programs will be available to allow the participation of students ranging from high school to graduate level. These are in particular NSF?s Research Experience for Undergraduates (REU) and the Vanderbilt Center for Science Outreach High School Summer Internship. Intellectual infrastructure of this project is expected to aid in the development of new magnetic and magneto-optical nanodevices.
Nanotechnology continues to produce important and unsuspected results, many of them for the benefit of mankind. Its potential is still being exploited and its development will likely continue within the foreseeable future. As structures and devices become smaller and smaller, the properties of the materials from which they are made change?in many instances dramatically?and differ from the properties of the bulk. Understanding these properties is very important to continue the development of technologies and the understanding of physical phenomena at smaller and smaller scales. On this light, this project aims at determining how geometry and magneto-optical effects are correlated in a class of ferromagnetic nanomaterials: the rare earth chalcogenides. When prepared using the specific methods of this project, these materials form in very small nanoparticles, some of which are so small that cannot be understood using classical physics, but require the use of quantum mechanics. Others (somewhat bigger, but still at the nano scale) form nanocrystals whose physical properties can be vastly different from those more familiar crystals formed by the material in bulk. The project seeks to understand the physics behind these differences by using magnetic, optical and x-ray diffraction, techniques. The intellectual infrastructure of this project is therefore expected to aid in the development of new magnetic and magneto-optical nanodevices sometime in the future. The different tasks and project activities are designed with the goals to encourage the participation of underrepresented groups in science, contribute to science infrastructure and integrate science and education. Educational/research programs will be available to allow the participation of students ranging from high school to graduate level. These are in particular NSF?s Research Experience for Undergraduates (REU) and the Vanderbilt Center for Science Outreach High School Summer Internship.
The primary goals of this research project involve understanding how very small magnets, called nano-magnets, can be made efficiently for use in consumer and industrial devices, like efficient telecommunications devices or magnetic hard drives for computers. We decided to pursue these research goals by studying the behavior of a unique category of objects, nanomaterials that are comprised of rare earth materials. Rare earth materials are substances that are made of elements in the period table that are called lanthanides. The lanthanides, because of their atomic structure, have optical, magnetic, and chemical reactive properties, are unique among all other elements. Therefore, studying such materials at the nanoscale provides a very advantageous position to study and to discover characteristics that could be exploited for the aforementioned device applications. Our work focused on the synthesis and characterization of spherical and rod-shaped nano-magnets comprised of europium sulfide (EuS), europium telluride (EuTe), and lead europium sulfide (PbxEuyS). Along with conducting these research activities, we were involved in promoting the education and research participation of high school and undergraduate research assistants working in a mentee-mentor partnership with graduate students within my group and with me. One of our major discoveries during this research project was world’s first synthesis and characterization of the magnetic properties of europium telluride (EuTe) nano-magnets (Figure 1). This finding has significance both in the scientific community’s understanding of magnetic interactions at the nanoscale, through the observation of an extremely rare phenomenon called superantiferromagnetism, and in the community’s view of use of these nanomaterials in devices. Here is why; EuTe is an antiferromagnetic material at very large sizes (what we call macroscopic sizes). This means that the material exhibits weaker magnetic properties when placed in a very large magnetic field. However, when made as a nano-magnet, the magnetism in the object becomes notably stronger. This was not expected, taking conventional wisdom and the existing theory of magnetism for rare earth materials. We call this unexpected magnetic response called superantiferromagnetism. Not only has this project led to exciting discoveries in the physics of magnetism, but the project also has allowed us to train the next generation of scientists proficient in nanoscience and magnetism. Training young scientists in this vibrant, emerging field bodes very well for continuing the United States’ leadership in science and engineering (Figure 2).
