Turbulent Transitions and Frustrated States: Some Issues in Reversal

A trend over the last few decades in many areas of science and technology has been to modify and control material properties through careful choice of dimensions. A key feature of such endeavors is to create useful physical properties governed by surfaces and interfaces. Important length scales in magnetic metals are spin diffusion, which ranges from angstroms to nanometers, and exchange lengths, which can be on the order of several nanometers. Advanced techniques now allow us to create structures on these length scales in three dimensions. This is a remarkable achievement because it often represents true atomic level engineering, and is based on years of detailed study of thin films and multi-layers.

A rich wealth of fascinating phenomena has emerged from studies of these types of constrained geometry structures within the contexts of high speed magnetization reversal and magnetic domain stability. This lecture will provide an introduction to essential concepts, illustrate examples of new physics, and present some challenging, unanswered questions. Topics will include examples of frustration in exchange bias systems and analogies to spin glasses; control of nonlinear processes in patterned magnetic structures and parametric processes incurred during high speed reversal; pinned and viscous domain wall motion in ultra-thin films and nanowires; and electronic and spin wave transport through domain walls. These examples will illustrate reversal processes and domain stability issues relevant for a wide variety of magnetic device applications, including concepts being explored for novel spin logic schemes.