New structures in intermetallic magnets related to Heusler compounds

1. New structures in intermetallic magnets related to Heusler compounds Ram Seshadri, University of CA - Santa Barbara, DMR 0449354 Research: Intermetallic compounds with the Heusler and half-Heusler crystal structures have been examined for half-metallic behavior, wherein all the states at the Fermi energy belong to only one spin direction. This property is of both fundamental interest as well as of technological importance in spin-based electronic devices, including devices for data storage and various kinds of motion sensors. Many magnetic Heusler compounds have as component elements, a magnetic transition elements such as Mn, a late transition element such as Pd, and a main group element. In order to separate the effects of structure from constitution in these compounds, we have prepared and studied by single-crystal X-ray methods, new compounds in the Pd-Mn-Si and Pd-Mn-Ge systems with structures derived from Fe2P. The structure is shown alongside, as is a depiction of the spin density in the Pd-Mn-Si compound. It is seen that the magnetism is localized on the Mn atom in this compound. S. Thimmaiah, C. Felser, and R. Seshadri, Crystal structure, magnetism, and bonding of the hexagonal compounds Pd1.63Mn0.37Si and Pd1.82Mn0.18Ge related to the Fe2P structure, J. Phys. D.40 (2007) 3915-3920.

2. New structures in intermetallic magnets related to Heusler compounds • Ram Seshadri, University of CA - Santa Barbara, DMR 0449354 Broader Impacts: Relating structure to property is a key aspect of the research in this proposal. In the state of California, Grade 8 science standards include the teaching of how structure can affect property like the strength of materials. Based on this, an activity for local 8th Graders has been devised around the forms of carbon, their structure, and their properties. Why is diamond hard, graphite soft, and C60 soluble ? Approximately 150 grade 8 students in three different centers in Santa Barbara and Ventura counties have attended the activity in summer ‘07.