Controlling Multiple Domain Walls in Ferromagnetic Nanowires with Magnetic Fields Studies by Micromagnetic Simulation

Marquette University, Milwaukee WI

Investigators

Abstract

TECHNICAL SUMMARY This award supports computational and theoretical research on magnetization dynamics in magnetic nanostructures that is integrated with undergraduate student education. This project aims to advance the understanding of the interaction between the magnetic state and the surface of nanoscale structures, in particular, the dependence of domain wall positioning due to defects and other domain walls inside the material. Many magnetic devices for recording, sensing, and logic operations have been proposed in which the motion and control of a domain wall in a nanowire is a necessary operating condition. Most of these proposed devices require the control of individual domain walls in the presence of others within the same structure which necessitates the need for understanding the important interactions taking place. The project will engage undergraduate physics majors to participate in carrying out computer simulations. Students will benefit from the research experience, and in the process, add to their education in magnetic materials and nanotechnology. New theories and computer simulations will be employed to understand and predict the behavior for control of the multiple magnetic domains that exist in nanowires. This work employs micromagnetic simulation methods to help test and validate theories and aid in the interpretation of experiments on motion of the magnetic domains. The combination of nanometer spatial resolution with concurrent picosecond temporal resolution makes micromagnetic simulation an ideal method for studying the field driven domain wall motion in a magnetic nanowire. Dynamic observation of domain wall motion in a magnetic nanowire is difficult experimentally due to the small size of nanowires. Investigations will yield techniques to manipulate individual domain walls in the presence of other walls without the loss of critical information. Ultimately this work impacts the viability of the proposed devices and increases the base of knowledge about magnetization dynamics in nanostructured materials as opposed to bulk materials. NONTECHNICAL SUMMARY This award supports computational and theoretical research that is well integrated with undergraduate student education. In this initiative research and education are developed to advance the theory of and the use of computers to simulate magnetic materials for nanoscale recording devices. Research efforts concentrate on understanding and advancing the manipulation of magnetic materials in nanostructures that are needed to understand and control magnetic devices and to promote their future use in high density and extremely fast magnetic recording devices. The project engages undergraduate physics majors to participate in carrying out the computer simulation and theoretical modeling. Students benefit from the research experience which in the process adds to their education in magnetic materials and nanotechnology. Some of the simpler interpretations and results are used for current topics in introductory courses to highlight the importance of classical physics in modern research and technology. New theories and computer simulations are employed to understand and reliably control the individual magnetic regions that can be created in nanodevices. The motion of these regions is being investigated by experiments and theories because of the potential application in extremely fast and small magnetic storage and sensing applications. This project employs computer simulation methods to help test and validate theories and aid in the interpretation of experiments on motion of the magnetic regions. Computer simulation is the only technique which gives simultaneous access to space and time in such small structures. The results of the proposed simulations are also important to understanding how to manipulate the location of a particular magnetic region in the nanowire which is then the basis for switching and logic. Reliable control of the magnetic region location and motion in magnetic nanodevices is essential to future generations of magnetic hard drives, as well as the logic devices. Manipulating the motion could lead to the creation of variable magnetic field sensors which depend on the magnetic domain location or number of domains.