Magnetization dynamics in lithographically patterned Ni80Fe20/Ir20Mn80 exchange-biased square elements




Xu, Haitian

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The magnetic properties and crystal texture of micron-sized, lithographically patterned ferromagnetic/antiferromagnetic (FM/AF) exchange-coupled elements supporting vortex remanent magnetization states were characterized using experimental and numerical modeling techniques. 10umx10um square elements consisting of Ni80Fe20/Ir20Mn80 bilayers prepared on silicon and glass substrates using e-beam lithography and magnetron sputtering were thermomagnetically annealed under various in-plane cooling fields to induce exchange bias. Longitudinal and time-resolved Kerr effect microscopy were employed to measure the quasi-static hysteresis and dynamic response, while X-ray diffraction analysis was used to probe their crystal texture under different deposition and substrate conditions. The FM layer was found to be critical for the development of the necessary texture and spin alignment in the AF for creating interfacial exchange-bias. The exchange-bias field was found to significantly alter the magnetic behavior of the samples, leading to the stabilization of the vortex structure and asymmetric hysteresis loop shift in the quasi-static regime, as well as precessional frequency reduction of the bottom domain in the dynamic regime. Numerical simulations showed good qualitative agreement with both experimental observations and existing literature, and revealed the origin of the precessional frequency reduction as the different spin-wave eigenmodes excited by different remanent magnetization states.



Exchange-bias, Magnetization dynamics, Vortex magnetization, Time-resolved magnetic microscopy, Numerical modeling