Hybrid Design for Advanced Magnetic Recording Media: Combining Exchange-Coupled Composite Media with Coupled Granular Continuous Media

Abstract

In order to enhance the performance of advanced granular recording media and understand the physics behind the mechanism of the reversal process, an atomistic spin dynamics simulation is used to investigate theoretically the magnetic properties and the magnetization reversal behaviour for a composite media design. This model allows to investigate the efect of the magnetostatic interaction and inter/intra layer exchange coupling for realistic system. The composite granular medium investigated consists of hard and soft composite layers in which the grains are well segregated with a continuous layer capping layer deposited to provide uniform exchange coupling. We present a detailed calculation aimed at revealing the reversal mechanism. In particular, the angular dependence of the critical ield is investigated to understand the switching process. The calculations show a complex reversal mechanism driven by the magnetostatic interaction. It is also demonstrated, at high sweep rates consistent with the recording process, that thermal efects lead to a signiicant and irreducible contribution to the switching ield distribution.

Magnetization dynamics of granular heat-assisted magnetic recording media by means of a multiscale model

“…The continuous increase in the virtual data generated by computers and mobile devices is pushing the limit of the current storage technology and alternatives are required. Current hard disk drives are able to reach areal storage densities up to about 1 Tbin −2 [1,2] with perpendicular magnetic recording (PMR) technology but face limitations to increase it beyond this point due to the so-called "magnetic recording trilemma" [3]: to further increase the areal storage density of recording media, smaller grains are needed; these grains need to have a high magnetic anisotropy [4] to be thermally stable; to write these high anisotropy grains, large head fields are required and these cannot be provided by a conventional write head. Heat assisted magnetic recording (HAMR) [1,[5][6][7] represents the most promising alternative to conventional magnetic recording.…”

“…Despite HAMR being proposed and investigated for around 15 years, a complete understanding of the functioning of these devices necessary for the introduction into the market is lacking [2,[12][13][14][15][16]. Moreover, engineering the medium by combining ferromagnets with different properties [4,17] and improving the head design can yield further increase in the storage density without compromising the reliability of the device [18]. In order for HAMR to be reliable, it is necessary that grains adjacent to the targeted region are not affected during the writing process.…”

Granular micromagnetic model for perpendicular recording media: quasi-static properties and media characterisation

“…We have applied the granular model of recording media to investigate the magnetic properties and in particular the effects of anisotropy dispersion and the microstructural design such as magnetic grain size, film thickness and grain size distribution. The results are of interest for the investigation of both the commonly magnetic materials as CoPt-alloy used in current recording technologies [12] for media and HAMR applications.…”

“…In this work, we generate a series of microstructures with specified grain size and size distribution as found in realistic recording media [14,20,21,22]. Here, we consider specifically a CoPt-based alloy [12], although the model is also applicable to the static properties often used to characterise HAMR media. We study a system with uniform grain size distribution.…”

“…In order to understand the magnetisation reversal behavior for advanced recording media with small grain size, the angular dependence of the critical field, H cr [12] as a function of film thickness is investigated, including the magnetostatic field, intergranular exchange field and the thermal effects at room temperature 300 K. Moreover, the easy axis dispersion expected to affected the magnetisation reversal behavior is also studied. In order to determine the effect of easy axis distribution, the comparison angular dependence of H cr at the perfect alignment case, σ φ = 0 • and small easy axis distribution, σ φ = 3 • is performed as Figure 5.…”