Bimodal properties of a patterned magnetic nanostructure: Separation of individual components’ contributions

• Magnetic nanoislands with perpendicular magnetization are studied by MOKE and MFM.
• A simple model to extract magnetic properties of the system components is used.
• Fitting conditions of the component hysteresis loops are discussed.
• Magnetization reversal of the nanoislands and the matrix and their coupling are deduced.

We study the properties of magnetic islands with perpendicular magnetization (dots), hundred nanometres in lateral size, embedded in a magnetic matrix, by magneto-optical method exploiting Kerr effect and magnetic force microscopy. Due to a complex structure the investigated patterned system displays a bimodal character. In order to gain an insight into behaviour of the components we apply a simple approach for decomposition of bimodal hysteresis loops obtained from magneto-optical measurements. The hysteresis loops of subsystems are determined from the field dependent rotation of a plane polarization and ellipticity of a laser beam reflected from the sample surface. Comparison with the adequate reference samples reveals differences in the behaviour of the patterned system resulting from confined size of the dots and their dipole coupling with the matrix. Magnetization reversal mechanisms of the individual components are discussed in details.