Magnetic Properties of NiFe Needles on Nanoporous Anodized Aluminum Oxides

In this study, a simple approach combining nanoporous templates with sputter deposition to obtain nano-sized permalloy structures is presented. The grain evolution and the corresponding magnetic anisotropy of permalloy films grown on the nanoporous anodized aluminum oxide (AAO) substrates with different deposition time were investigated. A grain evolution from a needle-like structure to a 2-D network was observed. As a consequence, the magnetization reversal of the permalloy films varied with the grain evolution. The magnetic domains of the permalloy films were pinned dominantly by the needle-like grain structure at the beginning; then, as the deposition time got longer, the domain sizes were constrained mainly by the underlying AAO network.