Two-Step Resist Deposition of E-Beam Patterned Thick Py Nanostructures for X-ray Microscopy

Abstract

Patterned elements of permalloy (Py) with a thickness as large as 300 nm have been defined by electron beam lithography on X-ray-transparent 50 nm thick membranes in order to characterize their magnetic structure via Magnetic Transmission X-ray Microscopy (MTXM). To avoid the situation where the fragility of the membranes causes them to break during the lithography process, it has been found that the spin coating of the resist must be applied in two steps. The MTXM results show that our samples have a central domain wall, as well as other types of domain walls, if the nanostructures are wide enough.

Bloch points and topological dipoles observed by X-ray vector magnetic tomography in a ferromagnetic microstructure

“…1). This field preparation favors the independent nucleation of reverse domains at different points in the permalloy boomerang 32,34 and, hence, the observation of transitions between different equivalent domain wall configurations in the final remanent state.…”

“…We have prepared an elongated boomerang microstructure (see Fig. 1) in which the typical flux closed domain structure favors the presence of a long central wall at remanence 32 . Sample thickness was chosen well above 50-60 nm, the thin film limit of symmetric Néel walls in extended permalloy films 33 and of transverse/vortex walls in permalloy nanostrips 34 .…”

“…Sample preparation. A 140 nm thick permalloy (Ni 80 Fe 20 ) boomerang microstructure was fabricated by e-beam lithography, DC magnetron sputtering and liftoff 32 . The substrate was a commercial Si 3 N 4 membrane (Ted Pella, 21501-10) with 50 nm thickness and 750 μm × 750 μm size.…”