The ferromagnetic metal/insulator interface: The implications for magnetic tunnel junctions.

摘要

A ferromagnet/insulator/ferromagnet sandwich (a.k.a. magnetic tunnel junction), with the insulator thickness at 25 A or less, allows for spin dependent tunneling events. The manipulation and harvest of these "events" leads to a magneto-resistive junction with applications in magnetic random access memory and picotesla magnetic field sensors. To understand the problems which prevent or preclude magnetic tunnel junctions from immediately appearing in our desktop computers, knowledge of the influence of the ferromagnet/insulator interface on the tunneling electron scattering and the spin dependent reservoirs must occur.; This thesis demonstrates that studies of semiconducting boron carbide, although it is a non-ideal tunnel barrier, may provide insight into the role of defect mediated spin polarized tunneling. The core of this thesis shows that the insulating organic self assembled monolayers, biphenyldimethyldithiol and biphenyldiisocyanide, may provide a very promising means of obtaining high tunnel magnetoresistance without the necessity of employing half-metals. The promise is related to the orientation of the molecules, the resultant structure they form, their insulating properties, their strong bond strength to cobalt surfaces, their hybridization type and predictions from theory which imply an induced magnetic moment from the metallic ferromagnet into the paramagnetic insulator at the interface.