Local-density calculations of the magnetic and paramagnetic phases of TmSe and TmTe.

Abstract

Results of local-density calculations are reported for both the paramagnetic and antiferromagnetic phases of mixed-valence TmSe. In the magnetic calculation, orbital moment effects are included self-consistently. Comparison of specific-heat data to the band density of states of the paramagnetic phase indicates a mass renormalization factor of 4.6, similar to what is seen in mixed-valence ${\mathrm{CeSn}}_{3}$. The moment-polarized calculation yields a total moment of 4.1${\ensuremath{\mu}}_{B}$, and an 86% gapping of the Fermi surface through the magnetic phase transition. The moment value is not consistent with the observed low-field-phase value of 1.7${\ensuremath{\mu}}_{B}$, but is consistent with the one in the higher-field metamagnetic phase. We also show evidence that the prediction of incomplete gapping of the Fermi surface is not inconsistent with specific-heat and resistivity data. Finally, we find that the insulating gap seen in TmTe can only be reproduced in a calculation where the f electrons are treated as core states.