Effect of pressure on antiferromagnetic transition in alkali-electro-sodalite

Pressure (0-19 kbar) and temperature (4-300 K) dependent EPR study of Sodiu m-Electro-Sodalite (SES) is presented. SES, which consists or a bcc sub-lat tice of F-centers supported by a zeolite-like framework, is known to be a M ott insulator at room temperature. On cooling, SES undergoes an AF transiti on at 48+/-2 K providing the first example of an s-electron antiferromagnet . We find that the width of the EPR resonance above T-N is influenced not o nly by a strong exchange interaction, but also by a fast spin-lattice relax ation. Also, with increasing pressure, T-N decreases linearly and extrapola tes to 0 K at about 65 kbar. The reason for this seemingly unexpected behav ior is briefly discussed.