X-Ray lithography patterning of magnetic materials and their characterization

Magnetic arrays of rectangular dots 1100 nm x 300 nm with 200 nm spacing (pattern a) and dots 800 nm x 550 nm with 200 nm spacing (pattern b) with the nominal thickness of 30 nm in Permalloy (Ni81Fe19) material were fabricated using X-ray lithography in combination of lift-off technique. A detailed magnetic characterization of the dot arrays was accomplished by magneto-optical Kerr effect investigations and micro-magnetic simulations, with emphasis given to the dependence of the hysteresis loop of the dots on their aspect ratio (shape anisotropy). In addition, the high frequency dynamical properties were probed by Brillouin light scattering (BLS) showing a marked discretization of the Damon-Eshbach surface spin-wave mode induced by the finite lateral dimensions. The measured frequencies compare fairly well to those calculated by an analytical method which considers spin waves confined in rectangular prisms.