Research on Nano-Magnetism.

 

R. A. Lukaszew, Ph. D.

 

Assistant Professor, Physics and Astronomy Department at the University of Toledo, Toledo, OH 43606

 

Magneto-transport studies in nano-structures are important for sensor applications. There have been several reports on domain-wall (DW) scattering effects in the magneto-resistance (MR) in magnetic thin films. Recent results on ballistic magnetoresistance (BMR) on electrochemically deposited nano-contacts have shown surprising MR values (> 3000% at RT). In an attempt to clarify some of the possible DW processes present in these phenomena, we have used e-beam lithography applied to epitaxial films to fabricate nano-bridges in more controlled geometry than that achieved with electrochemical deposition. Our studies have indicated that intrinsic DW mechanisms are observed in MR at room temperature in nano-contacts patterned on epitaxial Ni films. I will also show data on our additional structure-magnetic properties studies performed on epitaxial FeN thin films. Magneto-transport in nano-bridges made with these films was also investigated and indicated weaker DW effects on MR than what was observed for Ni. Aspects of this research have been funded by the AAAS.

I will also like to talk about the major recent research activities pursued in my group which are geared towards the study of magnetic binary alloys, particularly FePd and FePd and to the fabrication of thin films and nanostructures using these materials. Highly ordered L1_o thin films of these alloys exhibit very large magnetic anisotropy, and can be deposited with the anisotropy axis perpendicular to the film plane, making them suitable for example for perpendicular media. Currently, ion-implantation with large doses of Fe⁺ ions is being used in order to obtain nano-cluster formation of FePt nano-crystallites in a shallow region near the surface of eptiaxial Pt films. The samples will be further annealed in a novel process to be carried out at the Advanced Photon Source (Beam-time in March, 2005). This research is currently been funded by NSF, ACS and the Research Corporation.