EFFECT OF METAL DILUTION ON THE THERMAL AND LIGHT-INDUCED SPIN TRANSITION IN [FEXZN1-X(MTZ)6][CLO4]2 (MTZ=1-METHYL-1H-TETRAZOLE)

The thermal and light-induced spin transition in [FexZn1-x(mtz)6][ClO4]2 (mtz = 1-methyl-1H-tetrazole) was studied by Fe-57 Mossbauer spectroscopy and magnetic susceptibility measurements. The pure iron compound possesses two different lattice sites A and B for the complex molecules. At temperatures below 1 00 K a high spin (h.s.) --> low spin (l.s.) transition of the complexes at site A was observed, whereas the B molecules stay in the h.s. state at all temperatures down to 4.2 K. On isotypic dilution with zinc the spin transition was shifted to lower temperatures and became more gradual with decreasing iron content x of the mixed-metal crystals. At T less-than-or-equal-to 40 K the l.s.(A) state can be converted by green light into the long-lived metastable h.s.(A) state [light-induced excited spin state trapping (LIESST) (I --> h)] and the h.s.(B) state can be converted into a metastable long-lived l.s. (B) state using red light [LIESST (h --> 1)]. Reverse LIESST using red and green light, respectively, is possible in both cases.