An Ab Initio Study of Pressure-Induced Changes of Magnetism in Austenitic Stoichiometric Ni2MnSn

We have performed a quantum-mechanical study of a series of stoichiometric Ni2MnSn structures focusing on pressure-induced changes in their magnetic properties. Motivated by the facts that (i) our calculations give the total magnetic moment of the defect-free stoichiometric Ni2MnSn higher than our experimental value by 12.8% and (ii) the magnetic state is predicted to be more sensitive to hydrostatic pressures than seen in our measurements, our study focused on the role of point defects, in particular Mn-Ni, Mn-Sn and Ni-Sn swaps in the stoichiometric Ni2MnSn. For most defect types we also compared states with both ferromagnetic (FM) and anti-ferromagnetic (AFM) coupling between (i) the swapped Mn atoms and (ii) those on the Mn sublattice. Our calculations show that the swapped Mn atoms can lead to magnetic moments nearly twice smaller than those in the defect-free Ni2MnSn. Further, the defect-containing states exhibit pressure-induced changes up to three times larger but also smaller than those in the defect-free Ni2MnSn. Importantly, we find both qualitative and quantitative differences in the pressure-induced changes of magnetic moments of individual atoms even for the same global magnetic state. Lastly, despite of the fact that the FM-coupled and AFM-coupled states have often very similar formation energies (the differences only amount to a few meV per atom), their structural and magnetic properties can be very different

Pressure induced non-collinear magnetic structures in the Fe intermetallics

Results of the magnetic structure studies of R.sub.2./sub.Fe.sub.17./sub. intermetallics with non-magnetic R (R=Y, Ce, Lu) are summarized. Generalized phase diagram is obtained and discussed in terms of the anisotropic pressure induced changes of the interatomic distances

Planetary Mapping: A historical overview

The development of the methods of visualization, control, and content of planetary maps goes in parallel with terrestrial ones. Both reflect technological, scientific, sociopolitical, and graphic design changes. However, while terrestrial maps are ubiquitous and show abstract or iconic representations of the Earth features, planetary surfaces are much more frequently represented with uninterpreted images, despite the wealth of planetary spatial data. In this paper, we highlight the key maps and map series made before the space age and the new cartographic methods introduced in the early 1960s when rectified, geologic and airbrush maps, and space-borne planetary photography, revolutionized the way we can look at planetary surfaces. This chapter also highlights the most recent novel approaches in planetary cartography