Atomistic simulations of Heat-Assisted Magnetic Recording with longitudinal degrees of freedom

The advent of significantly advancing computational power has brought with it a new
challenge to grapple with: the amount of data being circulated, stored, and processed globally is increasing at unprecedented rates. While the demand for data storage has seen a clear rise, advancements to the magnetic recording devices utilised have also improved dramatically over the past few decades. Due to the limitations of conventional magnetic recording hard disk drives, reducing the size of the magnetic domains used to store information has become a challenge, and is approaching a hard limit. In order to combat this, Heat Assisted Magnetic Recording (HAMR) has shown great promise in overcoming the limitation in grain-size reduction by exploiting the temperature dependent properties of materials such as FePt to approximately quintuple the data storage density by the time HAMR is fully realised. In order to more appropriately research the exact optimisations necessary for HAMR, atomistic models are employed to simulate the recording process while having full control over the inter-atomic interactions governing the process. The theoretical modelling of materials such as FePt has shown inherent complexity regarding the treatment of the Pt atoms, as its inclusion in FePt’s magnetisation properties exists as an induced moment, brought on by the Fe exchange field. While the currently used atomistic model of FePt yields expected results, it fails to detail the truly atomistic nature of its behaviour, due to elimination of the Pt degrees of freedom. This thesis introduces the methods necessary to include maximal atomistic degrees of freedom in FePt, and demonstrates the viability of such a model in investigating the less looked at parts of theoretical HAMR, such as modelling the magnetisation of FePt with respect to its inherent disordering.