Giant magnetoresistance materials for magnetic recording technology

摘要

This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). This work focused on a class of transition-metal-oxide (TMO) materials (LaMnO{sub 3} doped with Ca, Ba, or Sr) that exhibits an insulator-to-metal transition near a ferromagnetic phase transition temperature. This yields a very large magnetoresistance; thus these materials may have important uses as magnetic sensors in a variety of applications, ranging from automobiles to read heads for magnetic storage. In addition, the transport current in the ferromagnetic state is likely to be very highly polarized, which means that additional device applications using the phenomena of spin-polarized tunneling can be envisioned. Use of these materials as magnetic sensors depends upon learning to control the synthesis parameters (principally temperature, pressure and composition) to achieve a specific carrier concentration and/or mobility. A second challenge is the high magnetic fields ({ge}1 Tesla) currently required to achieve a large change in resistance. The authors began an investigation of two novel approaches to this field-sensitivity problem, involving the development of multilayer structures of the TMO materials. Finally, they began to explore the use of epitaxial strain as a means of changing the transport properties in thin-film multilayers.