AVS 49th International Symposium
    Magnetic Interfaces and Nanostructures Thursday Sessions
       Session MI+NS-ThA

Paper MI+NS-ThA7
Magnetic Force Microscopy Study of Various Lithography Patterned Magnet Arrays

Thursday, November 7, 2002, 4:00 pm, Room C-205

Session: Magnetic Imaging
Presenter: X. Zhu, McGill University, Canada
Authors: X. Zhu, McGill University, Canada
P. Grutter, McGill University, Canada
V. Metlushko, University of Illinois at Chicago
B. Ilic, Cornell University
Y. Hao, Massachusetts Institute of Technology
F. Castano, Massachusetts Institute of Technology
S. Haratani, Massachusetts Institute of Technology
C.A. Ross, Massachusetts Institute of Technology
B. Vogeli, Massachusetts Institute of Technology
H.I. Smith, Massachusetts Institute of Technology
Correspondent: Click to Email
Magnetic force microscopy (MFM) with in-situ magnetic field has been used to study lithography pattered magnet arrays: elongated elements, rings, disks, empty squares and sub 100 nm pseudo spin valve structures (PSV) (NiFe/Cu/Co). Great care has been taken to reduce the MFM tip stray field induced irreversible distortion by choosing a constant height mode, using small magnetic moment tips, operating in vacuum, and using a digital PLL.@footnote 1@This allows us to study the details of magnetic structures. For example, the nature of the head-to-head domain wall in a permalloy ring can be revealed, and the vortex structure with a core singularity in a permalloy disk can be found by high resolution imaging. In the PSV structures, the parallel and two different antiparallel configurations for both magnetic layers (NiFe and Co) in an element can be distinguishable. A local hysteresis loop technique has been developed to study the switching behavior of individual elements.@footnote 2@ In a permalloy disk, the abrupt switching due to a nucleation or annihilation process has been revealed by monitoring cantilever frequency shift at a fixed location above the disk while sweeping the external magnetic field. In a PSV structure, the abrupt switching for both individual layers is clearly distinguishable. The hysteresis loop of patterned arrays can be obtained by MFM in the presence of an external magnetic field. The anisotropy induced by interdot coupling can be found in a closely packed square lattice disk array which shows a much smaller nucleation field along the (100) direction than the (110) direction. In the PSV structures, the layer coupling and the broad switching field distribution have been investigated through major and minor hysteresis loop obtained by MFM. @FootnoteText@@footnote 1@ X. Zhu, et al., J. Appl. Phys., May (2002). @footnote 2@X. Zhu, et al., to be published in Appl. Phys. Lett.