Magnetic Ring Devices for Memory and Logic

We are investigating the fabrication and magnetic properties of rings for magnetic logic and memory devices. The magnetic multilayer rings show giant magnetoresistance, in which the resistance is a function of the relative orientation of the magnetization directions in the magnetic layers. These small structures have potential uses in magnetic-random-access memories (MRAM), magnetic logic devices, and other magneto-electronic applications. Unlike that of conventional MRAM devices, the ring-shaped geometry of these devices allows for a complex response with multiple stable resistance states. This capability can be used for multi-bit memory and for programmable, non-volatile memory.

These devices are programmed using either a magnetic field or a current. We have shown that spin-polarized currents can reverse the devices by domain wall motion. We are currently investigating concatenation of multiple devices through stray field interactions and control of the behavior of individual devices through interlayer magnetostatic pinning interactions and manipulation of 360° domain walls with a spin-polarized current.

We are also investigating the effects of repeated cycling on rhombic ring devices. Stray field interactions between layers give rise to complex reversal paths, which depend on the field history. These complex reversal behaviors can be attributed to the formation of 360° domain walls and mirror domains in the structure. Understanding these interactions will facilitate the development of multilayer domain wall devices.