Measurements are reported on the magnetization reversal in submicron magnetic rings fabricated by high-resolution electron beam lithography and lift-off from cobalt thin films. For all dimensions investigated, with diameters of 300-800 nm and a thickness of 10-50 nm, the flux closure state is the stable magnetization configuration. However, with increasing diameter and decreasing film thickness a metastable near single domain state can be obtained during the reversal process in an in-plane applied field.
The magnetization reversal properties of high-resolution Co dot arrays fabricated by nanoimprint lithography have been studied as a function of both diameter and thickness. Both vortex and single-domain states were observed by measuring the hysteresis loops, which result in an experimental phase diagram in the diameter-thickness plane. In the vortex state, magnetization reversal proceeds by vortex nucleation, growth, and subsequent annihilation under relatively high field. The vortex growth has been shown to be reversible in a wide field range, in agreement with micromagnetic simulations. Finally, a distribution of annihilation fields in patterned dot arrays was studied experimentally.
We report the fabrication and magnetic properties of permalloy microgrids prepared by near-field optical lithography and characterized using high-sensitivity magneto-optical Kerr effect techniques. A fourfold magnetic anisotropy induced by the grid architecture is identified.
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