Out-of-Plane Magnetic Anisotropy in Ordered Ensembles of FeyN Nanocrystals Embedded in GaN

Phase-separated semiconductors containing magnetic nanostructures are relevant systems for the realization of high-density recording media. Here, the controlled strain engineering of GaδFeN layers with FeyN embedded nanocrystals (NCs) via AlxGa1−xN buffers with different Al concentration 0<xAl<41% is presented. Through the addition of Al to the buffer, the formation of predominantly prolate-shaped ε-Fe3N NCs takes place. Already at an Al concentration xAl≈ 5% the structural properties—phase, shape, orientation—as well as the spatial distribution of the embedded NCs are modified in comparison to those grown on a GaN buffer. Although the magnetic easy axis of the cubic γ’-GayFe4−yN nanocrystals in the layer on the xAl=0% buffer lies in-plane, the easy axis of the ε-Fe3N NCs in all samples with AlxGa1−xN buffers coincides with the [0001] growth direction, leading to a sizeable out-of-plane magnetic anisotropy and opening wide perspectives for perpendicular recording based on nitride-based magnetic nanocrystals.

Structural and Magnetic Properties of Rare Earth Doped Multilayer Nanocable Arrays

The structure and anisotropic magnetization of One-dimensional (1D) Nd/Co/PA66 coaxial nanocables prepared by a low cost physical infiltration and electrodeposition methods are investigated. The preparation of Co nanotubes, Co/PA66 two-layer nanotubes and Nd/Co/PA66 three-layer nanocales is described, respectively. The structure, chemical composition and magnetic properties of various nanomaterials were investigated. The results show that the magnetic properties were affected by the rare earth metal Nd and the structural properties. The residual magnetization ratio of Nd/Co/PA66 nanocables is the biggest due to the synergistic effect of Nd and Co. In addition, the magnetization processes of the nanostructure were discussed in detail. We believe that these methods may provide an idea for ferromagnetic alloys and permanent magnet material and suitable for future applications in perpendicular recording media.

Coupled Granular/Continuous Media – Results and Challenges

ABSTRACTWhile the most promising longitudinal recording systems cannot surpass the theoretical limit of about 200 Gb/in2 for areal recording density and the demand for higher densities is permanently increasing, the perpendicular magnetic recording constitutes the realistic issue to the longitudinal one. The perpendicular magnetic recording offers significant advantages, the most important being stronger write and read fields, and therefore the use of media of higher anisotropy, smaller grain size, higher signal-to-noise ratio, and a better thermal stability. Unfortunately, the perpendicular recording has to cope some important physical and technological difficulties. To overcome them, many ingenious solutions were proposed. In this paper the coupled granular/continuous (CGC) media, a subtle association of the continuous and, respectively, granular media, are analysed from the viewpoint of their magnetic and recording properties. The challenges and possible improvements of CGC media are discussed.