2D materials based ultra-thin memory storage: efficient energy conversion and novel device platforms

The family of two-dimensional (2D) materials has been growing fast since the isolation of Graphene, and so has the range of properties that can be explored in this low-dimensionality. Among such properties, magnetism was missing for a number of years, but a recent scientific breakthrough has introduced the first 2D, atomically thin, magnetic crystals in 2017. These atomically thin magnets find potential applications in the field of spintronics. In particular, transition metal thiophosphates such as MnPX3 (where X=chalcogen) are interesting candidates for antiferromagnetic spintronics. For these reasons, the aim of this project is to study the spin dynamics in 2D antiferromagnets such as MnPS3. We intend to understand the magnetic properties of 2D crystals and unveil the effect of different perturbations on them through Monte Carlo methods and Landau-Lifshitz-Gilbert (LLG) dynamics. This implies a description of the spin dynamics of systems with low dimensionality, including i) magnetic domains at different temperatures and material thicknesses; ii) domain wall motion in such materials, also considering different magnetic phases; iii) demagnetizing fields at different geometries and structure; and finally, iv) ultrafast spin dynamics induced by laser pulses and pulsed magnetic fields. In particular, the spin features in materials such as MnPS3 are intrinsically coupled to the crystal structure, resulting in different ground states, structures and spin configurations. This distinctive behaviour can be exploited in a variety of technological applications ranging from radiation-hardness, non-volatility, and efficient magnetic switching, up to ultra-fast writing schemes and novel information standards. Nevertheless, the interplay between different electronic quantities (magnetic moment, exchange, anisotropy) responsible for these unique features is not well understood at the limit of a single layer AFM magnet. This project intends to tackle this challenge through a multi-scale approach. Atomistic ab-initio calculations will be carried out to understand details of the atomic and electronic structure of the materials, as well as obtaining their intrinsic magnetic properties. Then, simulations of magnetic properties and spin dynamics will be performed at the micro-meter scale. Landau-Lifshitz-Gilbert (LLG) dynamics will be considered, based on the LLG equations, which determine the motion of the magnetisation in a solid considering the effective magnetic field as experienced by each atom. Thermal effects on the magnetic properties can be included through a Langevin mathematical treatment. This is a well-established approach to simulate spin dynamics at different dimensionality, systems and compositions. We expect that these micromagnetic simulations will broaden our understanding of these magnetic materials down to the monolayer limit, exploring their potential applications for memory storage purposes. Such insights will represent a step forward towards ultrathin antiferromagnetic spintronics. As part of this project, we will collaborate with the developers of VAMPIRE at the University of York. Any developments derived from these new approaches will be incorporated in the official version of VAMPIRE, thus making them available to other users.