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.
Rapid thermal annealing was applied to transform sputter-deposited Fe51Pt49/Cu bilayers into L10 chemically ordered ternary (Fe51Pt49)100−xCux alloys with (001) texture on amorphous SiO2/Si substrates. It was found that for thin film samples, which were processed at 600 °C for 30 s, the addition of Cu strongly favors the L10 ordering and (001) texture formation. Furthermore, it could be revealed by transmission electron microscopy and electron backscatter diffraction that the observed reduction of the ordering temperature with Cu content is accompanied by an increased amount of nucleation sites forming L10 ordered grains. The change of the structural properties with Cu content and annealing temperature is closely related to the magnetic properties. While an annealing temperature of 800 °C induces strong perpendicular magnetic anisotropy (PMA) in binary Fe51Pt49 films, the addition of Cu systematically reduces the PMA. However, due to the enhancement of both the A1-L10 phase transformation and the development of the (001) texture with increasing Cu content, lowering of the annealing temperature leads to a shift of the maximum perpendicular magnetic anisotropy towards alloys with higher Cu content. Thus, for an annealing temperature of 600 °C, the highest perpendicular magnetic anisotropy energy is found for the (Fe51Pt49)91Cu9 alloy. The smooth surface morphology, adjustable PMA, and high degree of intergranular exchange coupling make these films suitable for post-processing required for specific applications such as for sensorics or magnetic data storage.
A straightforward synthesis methodology for the preparation of rhodium(II) carboxylates [Rh 2 {O 2 CCH 2 (OCH 2 CH 2 ) 2 -OCH 3 } 4 ] n (1) and [Rh{μ-O 2 CCH 2 (OCH 2 CH 2 ) 2 OCH 3 } 2 -(PPh 3 )] 2 (2) is reported. The ethanol-mediated reduction of RhCl 3 ·3H 2 O with [K{O 2 CCH 2 (OCH 2 CH 2 ) 2 OCH 3 }] produced 1, which on further addition of PPh 3 afforded 2. Single-crystal X-ray diffraction studies of 2 were carried out showing a paddlewheel arrangement of the dirhodium(II) tetracarboxylate unit with a Rh-Rh distance of 2.4599(5) Å. Compounds 1 and 2 were applied in the formation of rhodium nanoparticles (NPs) using 1,2-ethanediol as reducing reagent and poly-(vinylpyrrolidone) (PVP) as capping component. Rhodium NPs with a narrow size distribution (Ͻ4 nm) were obtained [a]
SummaryThe most important limitation for a significant increase of the areal storage density in magnetic recording is the superparamagnetic effect. Below a critical grain size of the used CoCrPt exchange-decoupled granular films the information cannot be stored for a reasonable time (typically ten years) due to thermal fluctuations arbitrary flipping of the magnetization direction. An alternative approach that may provide higher storage densities is the use of so-called percolated media, in which defect structures are imprinted in an exchange-coupled magnetic film. Such percolated magnetic films are investigated in the present work. We employ preparation routes that are based on (i) self-assembly of Au nanoparticles and (ii) homogeneous size-reduction of self-assembled polystyrene particles. On such non-close-packed nanostructures thin Fe films or Co/Pt multilayers are grown with in-plane and out-of-plane easy axis of magnetization. The impact of the particles on the magnetic switching behavior is measured by both integral magnetometry and magnetic microscopy techniques. We observe enhanced coercive fields while the switching field distribution is broadened compared to thin-film reference samples. It appears possible to tailor the magnetic domain sizes down to the width of an unperturbed domain wall in a continuous film, and moreover, we observe pinning and nucleation at or close to the imprinted defect structures.
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