Abstract
The magnetic interlayer coupling of Fe19Ni81/Cu/Co trilayered microstructures has been studied by means of x-ray magnetic circular dichroism in combination with photoelectron emission microscopy (XMCD-PEEM). We find that a parallel coupling between magnetic domains coexists with a non-parallel coupling between magnetic domain walls (DWs) of each ferromagnetic layer. We attribute the non-parallel coupling of the two magnetic layers to local magnetic stray fields arising at DWs in the magnetically harder Co layer. In the magnetically softer FeNi layer, non-ordinary DWs, such as 270° and 90° DWs with overshoot of the magnetization either inwards or outwards relative to the turning direction of the Co magnetization, are identified. Micromagnetic simulations reveal that in the absence of magnetic anisotropy, both types of overshooting DWs are energetically equivalent. However, if a uniaxial in-plane anisotropy is present, the relative orientation of the DWs with respect to the anisotropy axis determines which of these DWs is energetically favorable.
Highlights
The magnetic interlayer coupling of Fe19Ni81/Cu/Co trilayered microstructures has been studied by means of x-ray magnetic circular dichroism in combination with photoelectron emission microscopy (XMCD-PEEM)
We find that a parallel coupling between magnetic domains coexists with a nonparallel coupling between magnetic domain walls (DWs) of each ferromagnetic layer
We have investigated the effects of stray fields and magnetic anisotropy in coupled FeNi/Cu/Co trilayered microstructures, especially in the vicinity of 90◦ DWs
Summary
Electron-beam lithography was employed to define the microstructures on top of a GaAs substrate. A parallel coupling between the two FM layers was introduced by the two-surface exchange term provided in the OOMMF package, using a bilinear surface exchange coefficient σ = 0.36 × 10−4 J m−2. This corresponds to a Néel coupling for a spacer thickness of 2 nm, with an interface roughness amplitude of 1 nm and a period of 10–20 nm, which is reasonable for our samples. For the rectangular structures, a small in-plane anisotropy field of 20 kA m−1 along the long edge of the structure was introduced to better adapt the simulation to the experiment
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