Berlin 2018 – scientific programme

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MA: Fachverband Magnetismus

MA 39: Micro- and nanostructured magnetic materials

MA 39.4: Talk

Thursday, March 15, 2018, 10:15–10:30, H 0112

FORC based interaction strength investigations in permalloy micro arrays — •Felix Groß, Sven Erik Ilse, Joachim Gräfe, and Eberhard Goering — Max-Planck-Institut für Intelligente Systeme, 70569 Stuttgart

First-order reversal-curves (FORCs) are a powerful tool to distinguish between microscopic interaction and coercivity contributions. However, most real systems usually violate Mayergoyz' congruency property which has to be fulfilled to easily interpret a FORC diagram. Investigating systems which violate Mayergoyz' criteria gives new fundamental insight into the FORC method. To build such a well-defined system, permalloy micro arrays of alternating width have been designed. By varying width and spacing, we are able to manipulate coercivities and interaction strength. Using a NanoMOKE3[1] we directly measure the low field spatially resolved switching field distribution, which shows binary distributed coercivities around 1 and 3 Oe. Surprisingly, an unexpected positive-negative peak pair appears at negative interaction fields in the FORC density. We could reveal that the two peaks are caused by interaction of high and low coercivity components. More precisely, by the interaction field which causes the small coercivity component to flip at different fields in parallel or antiparallel configuration. From the intensities of the peaks for different spacings, we can conclude, that turning off the interaction leads to fulfilled Mayergoyz' criteria again.

[1] J.Gräfe, Rev Sci Instrum, 85(2), 023901; 2014.