We have studied the magnetic interaction of circular magnetic islands with a dipole character on a square lattice. The square pattern consists of lithographically prepared polycrystalline PdFe islands, 150 nm in diameter and a periodicity of 300 nm. Below the Curie temperature at 260 K, the islands are in a single domain state with isotropic in-plane magnetization. Below 160 K, there is an onset of interisland interaction that leads to a change of the shape of the hysteresis, an increase of coercivity, and a development of in-plane anisotropy. Photoemission electron microscopy with circularly polarized incident x rays tuned to the L3 edge of Fe confirms the increasing correlation of the magnetic islands and the formation of elongated chains, as predicted by Vedmedenko et al. [Phys. Rev. Lett. 95, 207202 (2005)] for contributions from pole interactions of higher order than the dipolar one. Neighboring chains are found to be irregularly oriented either parallel or antiparallel.

We have studied the precessional dynamics of Co/Cu/Py (where Py = Ni81Fe19) trilayers by time-resolved x-ray resonant magnetic scattering at the synchrotron radiation facility BESSY II. We have found that the magnetic precessional decay time of Fe magnetic moments in Py layers decreases when changing the mutual orientation of the magnetization direction of Py and Co layers from parallel to antiparallel. The observed changes of the decay time can be associated with the spin pumping induced damping effect.

We investigated magnetic phase transitions, magnetic anisotropy, and magnetic domains in Pd1-xFex alloys with different Fe concentrations x = 2.2-7.2%. The Curie temperature depends linearly on the Fe concentration in the regime studied. The magnetization is dominantly in-plane with a small out-of-plane remanent contribution. Resonant magnetic small angle scattering with circularly polarized x-rays tuned to the L3 resonance edge of Fe revealed a small angle scattering ring corresponding to magnetic domain fluctuations on a length scale of 100 nm. These fluctuations are isotropically distributed in the film plane and appear to have an out-of-plane component. On increasing the transverse coherence of the incident beam, the scattering ring decomposes in a speckle pattern, indicative of magnetic correlations on a length scale smaller than the x-ray coherence length of about 4 μm.

The spin polarization of chromium at the interface next to a ferromagnetic layer is of general interest because of the competing ferromagnetic and antiferromagnetic exchange coupling. While the Fe/Cr interface has been well studied, information on the Co/Cr interface still remains scarce. Here we show for epitaxially grown Cr/Co/Cr(100) trilayers with smooth interfaces x-ray resonant magnetic scattering (XRMS) results in a saturation field of ±270 mT, recorded at the Co and Cr L 3 edges, respectively. The XRMS results at the Co edge show the expected asymmetry and a ferromagnetic hysteresis for different incident angles θ. Furthermore, XRMS measurements with the energy tuned to the Cr L 3 edge also exhibit an asymmetry, albeit much smaller than the one at the Co L 3 edge. Moreover, the magnetic hysteresis of Cr taken at the L 3 edge has a sign opposite to that of Co at the L 3 edge over a broad range of incident angles. From these results we infer first that at the Co/Cr interface chromium is ferromagnetically polarized, and second that its spin structure is oriented opposite to the magnetization of Co.

The spin structure and magnetization reversal in Co/Al2O3/Py triple layer nanodots have been investigated both via micromagnetic simulations and experimentally by magneto-optical Kerr effect measurements. Depending on the size, isolated Py dots show either a vortex state or single domain state during magnetization reversal. However, after combining the Py and Co dots in a stack separated by an insulating layer, the reversal process is governed by dipolar coupling between the soft and the hard ferromagnetic layer. Then, by means of micromagnetic simulations, we find either a stabilization and triggering of the vortex state or various types of buckling states. We construct a phase diagram, where regions for either states are marked depending on their respective layer thickness. We have studied two different types of systems with and without preferential anisotropy axis of the Co layer. The experimental results on systems with uniaxial magnetic anisotropy are found to behave as intermediate between these two numerical studies.