Pressure tuning of the exchange interactions between s-electrons in a bcc lattice of sodalite cages

Abstract

Néel (TN) and Weiss (⊖) temperatures of the alkali-electro-sodalites (AES) loaded with Na or K were investigated as a function of hydrostatic pressure up to 2 GPa with a low-frequency ESR technique. TN depends weakly on the pressure, but ⊖ decreases more sensitively with the pressure. The transfer energies t1 and t 2 via the two-kinds of coupling windows, hexagons and squares, respectively, are derived with the tight-binding and the two-sublattice molecular field approximations. Assuming that the transfer energies are suppressed by the pressure exponentially, the observed pressure dependence of TN and ⊖can be reproduced very well and suggested that the electronic states in Na-ES can be scaled to that in K-ES with a chemical pressure of ≈4 GPa. © 2003 Elsevier Science B.V. All rights reserved.