Magnetization, Magnetotransport and Ferromagnetic Resonance in A Permalloy Antidot Array with Square Holes

ABSTRACTA Permalloy antidot array with square hole size 800?800 nm2 has been fabricated by the means of electron-beam lithography and lift-off techniques. An out-of-plane anisotropy was found in both the reference film of Permalloy and the antidot array with the thickness of 100 nm. Inhomogeneous current-density distribution and complex domain structures in the antidot nanostructure result in unique behavior of the magnetoresistance. Quantized standing spin-wave modes originating from the lateral confinement of the antidot nanostructure were clearly observed for the magnetic field applied normal to the array plane. Two uniform precession resonance modes occurred when the field deviated more than 30 degrees from the normal to the plane. These two resonances originate from different regions of the array having distinct dipolar field patterns with different orientation and magnitude of magnetostatic field. The easy axes of the anisotropy in these regions are in-plane and orthogonal to each other.