Abstract
Full control of magnetic properties in exchange coupled systems requires a good understanding of 3D magnetic configuration with lateral and in-depth resolution. Here we show results from a soft X-ray tomographic reconstruction which allow determining, solely from the experimental data, a detailed description of the vector magnetic configuration of a ferrimagnetic Gd12Co88/Nd17Co83/Gd24Co76 trilayer with engineered competing anisotropy, exchange and magnetostatic interactions at different depths. The trilayer displays chevron patterns with a distorted closure structure. Near the top Gd24Co76 layer, local exchange springs with out-of-plane magnetization reversal, quasi-domains with ripple-like patterns and magnetic vortices and antivortices across the thickness are observed. The detailed analysis of the magnetic tomogram shows that the effective strength of the exchange spring at the NdCo/GdCo interface can be finely tuned by GdxCo1-x composition and anisotropy (determined by sample fabrication) and in-plane stripe orientation (adjustable), demonstrating the suitability of 3D magnetic visualization techniques in magnetic engineering research.
Highlights
1234567890():,; Advanced spintronic devices and magnetic recording media require control and characterization of multilayer magnetic systems in which the desired magnetic behaviour has to be precisely adjusted by properly tuning magnetic interactions such as exchange and magnetostatics[1,2]
Exchange springs are very interesting features to tune the magnetic behavior of a system: when two exchange-coupled magnetic layers have very different magnetic anisotropy[11], they originate characteristic domain walls at the interfaces to accommodate the reversible rotation of the soft magnetic layer under an applied field, while the hard layer stays pinned in its original magnetic configuration
We report the results of exploiting the capabilities of magnetic vector tomography to determine the magnetization of a complex magnetic trilayer engineered to have competing or favoring exchange/magnetostatic interactions at different depths
Summary
1234567890():,; Advanced spintronic devices and magnetic recording media require control and characterization of multilayer magnetic systems in which the desired magnetic behaviour has to be precisely adjusted by properly tuning magnetic interactions such as exchange and magnetostatics[1,2]. Exchange springs are very interesting features to tune the magnetic behavior of a system: when two exchange-coupled magnetic layers have very different magnetic anisotropy[11], they originate characteristic domain walls at the interfaces to accommodate the reversible rotation of the soft magnetic layer under an applied field, while the hard layer stays pinned in its original magnetic configuration They are versatile magnetic systems since they can be tuned adjusting the individual layer thickness and interlayer coupling strength[12,13,14,15,16,17,18,19,20]. Most of the previous studies are based in measurements of hysteresis loops and the domain structures, which are instrumental for the understanding magnetization reversal, are inferred indirectly from comparisons with micromagnetic simulations[18]. More detailed in-depth characterization of magnetization profiles of interfacial domain walls can be obtained by magnetic reflectometry with either neutron[20] or X-ray-based techniques[12,24,25] but mainly in systems with homogeneous or periodic configuration
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