Synthesis and Magnetic Properties of Transition Metal Phosphides

Stephanie L. Brock, Wayne State University, DMR-0094213According to general lore, the introduction of shape anisotropy into ferromagnetic systems results in augmented magnetic coercivity (i.e., a greater resistance to de-magnetization). This is the principle behind the use of nanorods for magnetic hard drive storage. However, examination of a range of data suggests that the actual coercivity values are all over the map, and that other influences may be at play. Using NSF funds, the synthesis of low-polydispersity MnP nanoparticles of rod shape has been achieved and the properties compared to spherical particles. The rods form as single crystals, and the rows of atoms are apparent as lines in the electron micrograph (right). Surprisingly, the introduction of shape anisotropy has no influence on the coercivity, and causes no actual change in the overall anisotropy of the system. These data suggest that the inherent magnetocrystalline anisotropy might be the dominant factor for the magnetic response, and that the relative strengths of different anisotropy factors dictates the extent to which coercivity can be tuned by shape.

5 nm

ba

c

(200)

High resolution TEM image of a MnP nanorod with lattice fringes corresponding to the (200) plane. The a, b, and c axes of the MnP unit cell are labeled and correspond to the hard, intermediate and easy axes, respectively, according to the preferred magnetic direction the spins align.

Introducing Nanomaterials to Undergrads: Getting students involved in Nanochemistry early in their studies is important for the development of this new interdisciplinary science, but is not addressed in traditional Chemistry curricula. Over the course of the CAREER proposal, three new laboratories and several lecture segments focused on nanomaterials have been integrated into the undergraduate inorganic courses at Wayne State. Additionally, a total of ten undergraduate students have participated in original research projects in the Brock lab. In the process, these students have acquired hands-on experience with state of the art instrumentation, including X-ray powder diffraction, and electron and atomic force microscopes.

Synthesis and Magnetic Properties of Transition Metal Phosphides

Stephanie L. Brock, Wayne State University, DMR-0094213

Michele Tague, an undergraduate from Keene State College, NH, and participant in the NSF Summer Research Program in Solid State Chemistry, seals a sample in a glass ampoule.

Synthesis and Magnetic Properties of Transition Metal Phosphides

Stephanie L. Brock, Wayne State University, DMR-0094213

Laboratories on ferrofluids, metal chalcogenide nanoparticles, and sol-gel chemistry have been added to the senior level undergraduate inorganic chemistry lab/lecture course. Additionally, modules on solid state structure, band theory, and physical properties of nanomaterials have been incorporated in both the sophomore and senior level inorganic chemistry courses.A total of ten undergraduates (including three current students and a 2004 summer fellow, Michele Tague) contributed to the NSF funded research. The most recent graduate, Christina Sweeney, participated in NSF Summer Research Program in Solid State Chemistry in 2004, working in the lab of Joanna Aitzenburg at Lucent Technologies. She is now a first year graduate student at Northwestern University and first author on a recently submitted manuscript.