Comprehensive Studies on the Magnetic Reversal Properties of Bilayered Magnetic Anti-Dot Lattices

In this work, we report the results of our study on the magnetization-reversal properties in a bilayered magnetic antidot lattice (BMAL) system consisting of upper perforated thick Co layer of 40 nm and lower continuous thin Ni layer of 5 nm, probed by using a superconducting-quantum-interference-device (SQUID) magnetometer and by magnetic-force microscopy (MFM). Such a BMAL structure was fabricated by using photolithography and controlled wet-etching processes. A systematic study on the in-plane anisotropy, and the switching-field properties was carried out. The atomic-force-microscopy (AFM) image clearly indicated that the anti-dot array structures are well defined, and the local element composition was confirmed by using the energy dispersive spectra (EDS). The room-temperature hysteresis curves, taken along different directions of the applied magnetic-field, were proved to be useful to understand the magnetic anisotropy in the sample. A kind of uniaxial anisotropy with easy axis along 0° and hard axis along 90° of applied field direction was observed. To get a comprehensive knowledge about the domain configuration, we performed the MFM imaging along the easy and hard axis of the lattice. The MFM images revealed well-defined periodic domain networks which can be ascribed to the anisotropies such as magnetic uniaxial anisotropy, configurational anisotropy, etc. The observed changes in the magnetic properties are closely related to the patterning that pins the domains as well as to the magneto-anisotropic BMAL structure.