PREDICTION OF PRESSURE-INDUCED CHANGES IN MAGNETIC-ORDERING OF CORRELATED-ELECTRON URANIUM SYSTEMS

Experimentally, hydrostatic pressure experiments provide a very sensitive way to probe the development of magnetic ordering in correlated-electron systems. We have now developed and applied theory allowing us to understand and quantitatively predict the variation of ordering temperature with pressure in uranium-based correlated-electron materials on a wholly predictive calculated basis, i.e., without using any experimental data as input in the calculation. The theory physically captures the changes in the f spectral density distribution in space and time that are driven by pressure-induced increased band-f hybridization. As a test case, we have predicted behavior in good agreement with experiment for UTe where experimentally (Link et al.) T(c) increases from 104 K to a maximum of 181 K at 7.5 GPa and then decreases to 156 K at 17.5 GPa. Our calculations: (1) using full-potential total-energy calculations match the experimental lattice parameter change with pressure within 2% and provide the decrease in average 5f-electron number; (2) extract information from the electronic structure calculation on the hybridization-induced changes and insert this into many-body theory to calculate the increase in two-ion coupling with pressure (from increased f spectral admixture into the bands) giving the initial increase in T(c); (3) calculate the decrease in ordering temperature (in terms of coupling) with decreased 5f number (localized spectral density) which gives the ultimate decrease in T(c).