Colossal magnetoresistance and re-entrant charge ordering in single crystalline two layer Mn perovskite LaSr2Mn2O7

We report on the resistivity (rho(ab)), magnetisation (M), and X-ray synchr otron measurements on a single crystal of the two-layer manganite LaSr2Mn2O 7. rho(ab) showed a maximum at 180 K and increased rapidly for T < 80 K. In a field of 8 T, colossal magnetoresistance (CMR) data showed two maxima at 150 and 40 K. In low fields, M (H parallel to ab) showed also two maxima a t these temperatures. X-ray investigations revealed satellite reflections w hose intensity showed a strong maximum at 170 K followed by a re-entrant be haviour below about 40 K. The data seem to reflect the structural, charge a nd orbital degrees of freedom present in this compound. (C) 1999 Elsevier S cience Ltd. All rights reserved.