Berlin 2015 – scientific programme

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MA: Fachverband Magnetismus

MA 19: POSTER Ia

MA 19.22: Poster

Tuesday, March 17, 2015, 09:30–13:00, Poster A

Investigation and optimization of magnetic properties of micro-patterned Permalloy structures for giant magneto-impedance sensors — •Gregor Büttel, Haibin Gao, and Uwe Hartmann — Institute of Experimental Physics, Saarland University, P. O. Box 151150, D66041, Saarbrücken, Germany

Permalloy (Ni81Fe19) structures were fabricated by lithography and dc magnetron sputtering. Aspect ratio and sputtering parameters were varied and their influence on domain structures and hysteresis were studied by vibrating sample magnetometry and magneto-optical Kerr effect microscopy in an applied external field. We obtained a very high Kerr contrast for Permalloy by post-processing data algorithms and sputtered dielectric coating layer. Coercivity and anisotropy were optimized by control of sputter rate, biasing field and magnetic annealing to yield soft magnetic films with a thickness between 200 and 1000 nm with low anisotropy, perpendicular to the long axis of the rectangular structures and to the underlying waveguide. The often reported perpendicular anisotropy and stripe domains above a critical thickness of the elements were found in our samples as well. The critical thickness changes slightly depending on the possible waveguide substrate like Cu, Au and Al vs. SiO2. However, we could obtain films without stripe domains and a transcritical shape of the hysteresis curve above a thickness of 500 nm by adjusting the sputter rate accordingly. For films within the thickness regime of 200-500 nm we could diminish strongly the transcritical shape of the hysteresis curve by magnetic annealing, although stripe domains remain.