| AVS 56th International Symposium & Exhibition | |
| Magnetic Interfaces and Nanostructures | Thursday Sessions |
| Session MI-ThP |
| Session: | Magnetic Interfaces and Nanostructures Poster Session |
| Presenter: | J. Bates, McGill University, Canada |
| Authors: | J. Bates, McGill University, Canada C.V. Cojocaru, McGill University, Canada Y. Miyahara, McGill University, Canada P. Grutter, McGill University, Canada |
| Correspondent: | Click to Email |
There is an ongoing interest in understanding the switching field distribution (SFD) of nanoscale patterned magnetic elements, which show great potential for novel applications such as magnetic quantum cellular automata [1] or magnetic random access memory [2] architectures. To make these architectures technologically viable, it is essential for patterned magnetic elements, to have a reproducible and controllable magnetic switching mechanism, thus a narrow SFD. Factors that affect the SFD are not known a priori and might be of various natures: thermal effects, shape, imperfections in fabrication, microstructure, edge roughness, seed-layer, anisotropy variations and magnetostatic interactions with neighbors etc.
To address these issues we used a combination of atomic/magnetic force microscopy (AFM/MFM) [3] and transmission electron microscopy (TEM) on indexed arrays of permalloy nanoscale structures, sputter-deposited via stenciling on ultra thin silicon nitride membranes. The stencil-masks used during the deposition process features ordered arrays of nano-apertures, prepared by focused ion beam milling. The stenciling process is parallel, resistless, and allows for the direct organization of structures having different aspect ratios (length/width) into any desired architecture.
Permalloy structures were characterized initially by AFM to assess their topography. Then MFM was used in constant height mode in order to obtain magnetic state (domains) and SFD of the structures. Magnetization reversal was studied by applying an in situ magnetic field parallel to the sample surface with a pair of rotating NdFeB permanent magnets. Structures with in plane aspect ratios below 4:1(400nm:100nm) revealed a multidomain state thus complex switching behavior, while structures with an aspect ratio above showed a bipolar state and switched coherently. Structures that switched at lower fields were identified as “early” switchers and structures that switched at larger fields were identified as “late” switchers. TEM images of the “early” and “late” switchers have been compared to normal switchers to look for structural variations, which may induce differences in behavior and broaden the SFD.
[1] R. Cowburn et al., NJP 1, 161(1999)
[2] B. D. Terries et al., J. Phys. D: Appl. Phys. 38, R199 (2005)
[3] X. Zhu and P. Grutter, Phys. Rev. B 66, 024423 (2002)