NSF: Magnetic Properties of Mesoscopic Multilayer Rings; 3D ferromagnetic ring device structures for spintronics.

The main aim of the research is to explore the fundamental magnetic, transport and collective properties of 3D multilayer structures and arrays. Such structures consist of ferromagnetic multilayers (typically 1-10nm thickness, fabricated from transition metals and alloys with non-magnetic layers as spacers) structured into rings down to 150nm diameter or smaller. The new class of structures presents significant fabrication, characterisation and measurement challenges which go well beyond the expertise of a single group but which we address in this proposal by building on the previous successful collaboration on single layer (2D) rings between the Cambridge and MIT groups. This previous collaboration has produced numerous publications in prestigious journals such as Phys. Rev. Letts. and the exchange of research students and postdoctoral researchers between the two groups which have been very fruitful and we expect this to provide a very strong base for the new collaboration. Specifically, the MIT group bring materials deposition and device fabrication expertise and expertise in device applications in spintronics to the project while the Cambridge group bring expertise in magnetic and optical measurements and in the interpretation of magnetic switching and dynamics. Together this makes a very strong team well suited to this ambitious project. We also propose to have several students and the post doctoral researcher involved participate in exchanges between the two institutions both to facilitate the research programme and to provide a training opportunity in an international context. Our goal is to create a novel 3D architecture based on multilayer ring structures, both as single entities and as arrays, in order to assess the potential of such structures for device and memory applications.