Dresden 2020 – scientific programme

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MA: Fachverband Magnetismus

MA 57: Posters Magnetism II

MA 57.15: Poster

Thursday, March 19, 2020, 15:00–18:00, P3

Relaxation behaviour of antiferromagnetic grains in polycrystalline exchange bias bilayers — •Maximilian Merkel, Rico Huhnstock, Meike Reginka, and Arno Ehresmann — Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), University of Kassel, Heinrich-Plett-Str. 40, D-34132 Kassel

The macroscopic magnetic characteristics of polycrystalline exchange bias thin films (antiferromagnet/ferromagnet) are mainly linked to the grain size distribution of the antiferromagnetic layer, which can be divided into classes of thermally unstable as well as thermally stable grains. These grain classes are connected to the coercivity and the horizontal shift (exchange bias field) of the ferromagnetic hysteresis loop, respectively. In order to tune the contribution of rotatable and pinning grains, sets of IrMn/NiFe and IrMn/CoFe bilayers with varying antiferromagnetic layer thickness were fabricated via sputter-deposition. Applying the first-order reversal curve (FORC) formalism, the distribution of coercivities and interaction fields of the granular systems have been determined complementary to angular-resolved hysteresis measurements using Kerr-magnetometry in comparison to an extended Stoner-Wohlfarth model. The combination allowed for the quantitative determination of material parameters and the deconvolution of grain class contributions. Additionally, by changing the sweep rate of the external magnetic field during a magnetization reversal process enabled the investigation of the relaxation times of the antiferromagnet's thermally unstable and therefore rotatable grains.