Exchange-coupled composite media were realized by combining perpendicular hard magnetic FePtCu alloy films with perpendicular Co/Pt multilayers which are magnetically softer. We demonstrate that the switching field of the hard layer can be efficiently altered by modifying the material properties of the soft layer by varying the number of Co/Pt bilayers. Moreover, the possibility of effectively tuning the interlayer exchange coupling using rapid thermal annealing was shown. These studies were supported by theoretical modeling revealing the relevant factors to reduce the switching field of the hard layer which are important for future media design.

We present a study on the magnetization reversal in Co/Pt multilayer films with an out-of-plane easy axis of magnetization deposited onto substrates with densely distributed perforations with an average period as small as 34 nm. Deposition of magnetic Co/Pt multilayers onto the nanoperforated surface results in an array of magnetic nanodots surrounded by a continuous magnetic film. Following the evolution of the magnetic domain pattern in the system, we suggest that domain walls are pinned on structural inhomogeneities given by the underlying nanoperforated template. Furthermore, a series of micromagnetic simulations was performed in order to understand the modification of the pinning strength of domain walls due to the magnetic interaction between nanodots and the surrounding film. The results of the simulations show that magnetic exchange coupling between the nanodots and the surrounding film strongly influences the pinning behavior of the magnetic domain walls which can be optimized to provide maximal pinning.

We present an analytical derivation of the switching field distribution (SFD) at finite temperature for a single domain particle from the Néel-Brown model in the presence of a linearly swept magnetic field. By considering the field dependence of the attempt frequency f0 in the rate equation, we find enhancement of coercivity compared to models using constant f0. The contribution of thermal fluctuations to the standard deviation of the switching field HC derived here reaches values of 10% HC. Considering this contribution, which has been neglected in previous work, is important for the correct interpretation of measurements of switching field distributions.

We report a finite temperature micromagnetic method (FTM) that allows for the calculation of the coercive field of arbitrary shaped magnetic nanostructures at time scales of nanoseconds to years.Instead of directly solving the Landau-Lifshitz-Gilbert equation, the coercive field is obtained without any free parameter by solving a non linear equation, which arises from the transition state theory. The method is applicable to magnetic structures where coercivity is determined by one thermally activated reversal or nucleation process. The method shows excellent agreement with experimentally obtained coercive fields of magnetic nanostructures and provides a deeper understanding of the mechanism of coercivity.

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