EPR STUDIES ON MOLYBDENUM PHOSPHATES MO2P4O15, NAMO3P3O16 AND BAMO2P4O16 IN THE TEMPERATURE-RANGE 300-4-CENTER-DOT-2K

EPR studies of molybdenum phosphates, Mo2P4O15, NaMo3P3O16 and BaMo2P4 O16 in the range 300-4.2 K was carried out. Delocalization of 4d(1) el ectron on a Mo5+ Site in the MoO6 octahedra occurs due to tunneling pr ocess. This gives rise to unresolved EPR lineshapes in all the cases e xcept in Mo2P4O15. The slight indication of hyperfine structure in Mo2 P4O15 is due to less feasibility of delocalization of the the 4d(1) el ectron, as MoO6 octahedron is connected through a PO4 group to only th ree octahedra as compared with higher numbers in the case of others. T he negative g-shift is observed in all the cases due to positive sign of the spin-orbit coupling constant. The decreasing trend in g(iso)-va lues in Mo2P4O15 and NaMo3P3O16 with decreasing temperature is observe d, whereas in BaMo2P4O16 the g(iso)-value increases with decreasing te mperature.