This proposal aims to investigate a class of frustrated magnetic materials called spin ices. The main goals are threefold. First, to investigate the specific relations for the internal and external susceptibility when comparing diffuse neutron scattering with direct magnetisation measurements using for example a superconducting quantum interference device. Second, to calculate the demagnetising factors
necessary for any quantitative study of magnetic susceptibilities in insulating magnets. Third, to establish a model for the spin ice Ho2Ti2O7 by the use of high resolution experimental neutron scattering data only via structure factor calculations. All three main goals of the project require large amounts of computing power in order to get viable results. We have developed several parallel computer codes which already have been tested to work sufficiently. One of the codes is a massively parallel Monte Carlo code capable of calculating the neutron structure factor for systems ten times larger than previously studied, with an equal increase in the spatial resolution. Of paramount importance in all parts of the project is a very close collaboration with our experimental
colleagues. In the collaborations we develop state-of-the-art computational tools to meet the many challenges encountered when investigating frustrated magnetic systems. Having completed the development of the program, a medium allocation on Beskow would mean that we can could calculate neutron spectra, demagnetizing factors and model parameters and publish the results of our current projects. This project is almost exclusively related to neutron scattering which is the main purpose of the European Spallation Source (ESS) under construction in Lund, and therefore of strategic importance to Sweden.
During 2018 our results so far in the project have been published in Nature Communications, 9, 1999 (2018) and Physical Review Letters 121, 067202 (2018), two high impact journals, where we properly referenced PDC.