  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.
