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We report on pairs of converging-diverging spin vortices in Co/Rh/NiFe trilayer disks. The lateral magnetization distribution of these effective spin merons is directly imaged by means of element-selective x-ray microscopy. By this method, both the divergence and circulation states of the individual layers are identified to be antisymmetric. Reversal measurements on corresponding continuous films reveal that biquadratic interlayer exchange coupling is the cause for the effective meron pair formation. Moreover, their three-dimensional magnetization structure is determined by micromagnetic simulations. Interestingly, the magnetic induction aligns along a flux-closing torus. This toroidal topology enforces a symmetry break, which links the core polarities to the divergence configuration.

Ferromagnetic Mn5Si3C0.8 and Mn5Ge3C0.8 films with Curie temperatures TC well above room temperature are obtained by C+12-ion implantation in antiferromagnetic Mn5Si3 or ferromagnetic Mn5Ge3. Patterning of the films with a gold mesh serving as a stencil mask during implantation allows a lateral modification of magnetic order creating ferromagnetic regions of Mn5Si3C0.8 which are embedded in antiferromagnetic Mn5Si3. This provides a procedure for the fabrication of magnetoelectronic hybrid devices comprised of different magnetic phases.

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The influence of a nanoscale surface modulation periodicity of ion beam eroded substrates ͑ripples͒ on the interlayer exchange coupling in polycrystalline Fe/Cr/Fe thin films is investigated. Using 22 nm rippled substrates, we find a pronounced Néel coupling superimposed on the interlayer exchange coupling in Fe/Cr/Fe trilayers associated with a strong uniaxial anisotropy induced by the substrate topography. For longer periods the Néel contribution and uniaxial anisotropy become weaker and finally vanish in the case of a flat substrate and film. These results are obtained by applying a Stoner-Wohlfarth model on magnetic reversal loops measured by longitudinal magneto-optical Kerr effect magnetometry.

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We study field- and current-induced domain-wall motion in permalloy nanowires containing a square-shaped magnetically softened region. Implantation of chromium ions is used to induce pinning sites via a local reduction in the saturation magnetization. Micromagnetic simulations, magnetic transmission soft x-ray microscopy, and electrical measurements are employed to characterize the pinning potential which significantly differs for transverse and vortex walls. Reliable domain-wall depinning from a so-called magnetic soft spot by single current pulses is observed. This demonstrates the suitability of these pinning sites for applications.

We report on both the global and micromagnetic properties of interlayer exchange coupled spin systems. Irradiation with Ne ions is employed to achieve a phase transition from antiferromagnetic to ferromagnetic coupling. For extended trilayer films a full quantitative analysis of the bilinear and biquadratic coupling constants is performed. With increasing ion fluence we observe a steady increase of the bilinear coupling constant at an almost negligible decrease in saturation magnetization. The mixing of atoms at the layer interfaces is identified as the origin for this. The effects of ion modification on the magnetic microstructure are studied for the model system of layered vortex pairs. X-ray microscopy is used to directly image the individual magnetization circulations in trilayer disks. The circulation configuration is found to be determined by the film coupling for both coupling orientations with a homogenous coupling angle throughout the structure. For the vortex cores, however, micromagnetic simulations indicate that due to the significant local demagnetization fields, parallel states are always energetically preferred. Nevertheless antiparallel configurations are metastable, having their signature in reduced core diameters. Our study provides new results on spin structures in interlayer exchange coupled trilayers and it demonstrates a promising way to control the local interlayer coupling post-deposition.