Description

2D magnetic materials have sourced great attention in the last few years. Intrinsic theoretical interest arises from the very existence of magnetism below the 3D limit, which has been proven only recently after decades of debate, as well as from the observed richness in magnetic phases, encompassing conventional ferromagnetic and antiferromagnetic as well as more exotic textures. Besides, these materials are known to offer practical applications in fields, such as spintronics and quantum technology. The popularity gained by such research field has motivated the optimization of computational approaches to evaluate exchange parameters, needed for the prediction of magnetic textures. However, the methodology is not uniquely established as of today, which results in a lack of systematicity in the data produced; as a consequence, contrasting predictions may arise, sometimes preventing a full comprehension of the nature of exchange interaction.
The present thesis work, to be carried out under the supervision of Dr. Silvia Picozzi (Consiglio Nazionale delle Ricerche CNR-SPIN, Research Unit located at Università degli Studi Gabriele D’Annunzio - Chieti), consists in performing numerical simulations aimed at extracting exchange parameters for selected 2D magnets. This will be done by exploiting the expertise peculiar to the CNR-SPIN group, i.e., within the framework of Density Functional Theory (DFT), the most popular technique for first-principles simulations in the condensed matter community, plus a suitable mapping of DFT results to a model Heisenberg-like Hamiltonian.
The outcomes of the work will help shed light on the nature of exchange interactions in some debated cases, as well as constituting the building block for a 2D exchange constants database, which may well bring about the possibility of publishing the results in a dedicated paper.

Timeline

4-6 weeks: getting acquainted with Density Functional Theory, its practical application with the VASP software and model Hamiltonians for non-collinear magnetism including spin-orbit effects
16-18 weeks: execution of a Python-based workflow that automates DFT simulations of first, second and third nearest-neighbor exchange parameters for selected materials; interpretation of the results. The workflow is already at disposal in a working form, but may of course benefit from refinements and extensions, in case this matches the candidate’s skills

Required skills

Required: Quantum Mechanics, general Solid State Physics, basics of magnetism in matter
Useful: basics of Linux OS and Python language (these can anyway be achieved along the way)

Expertise to be gained during work

Essential knowledge of DFT; ability to prepare and run DFT simulations; use of high-performance computing resources; thorough understanding of exchange mechanisms and related model Hamiltonians

Logistics

It is very advisable to spend at CNR-SPIN in Chieti a short period (1-2 weeks) at the beginning of the thesis, when the candidate will most likely need to be supervised from a close distance. After that, the work might be carried out remotely. Occasional visits of CNR-SPIN group members to Milan are possible as well.

Supervisors

PoliMi supervisor: Prof. Christian Rinaldi, External supervisor: Dr. Silvia Picozzi.
For further information, do not hesitate to contact Dr. Picozzi at silvia.picozzi@spin.cnr.it . Additional info on the research group is available at https://sites.google.com/site/silviapicozzi/