Extending the n=2 Ruddlesden-Popper Solid Solution La2-2xSr1+2xMn2O7 Beyond x=0.5: Synthesis of Mn4+-rich Compounds

We report the synthesis and room temperature crystal structures of the heretofore unknown, metastable manganites La2-2xSr1+2xMn2O7+delta (0.5 < x < 0.9) via high-temperature (T=1650 C) quenching followed by low-temperature (T=400 C) annealing to fill oxygen vacancies; this approach enables access to the electronic, magnetic, and structural properties of previously unexplored compositions in this important CMR system.