FERROMAGNETISM-INDUCED REENTRANT STRUCTURAL TRANSITION AND PHASE-DIAGRAM OF THE LIGHTLY DOPED INSULATOR LA1-XSRXMNO3 (X-LESS-THAN-OR-EQUAL-TO-0.17)

The crystal structure of the lightly doped insulating system La1-xSrxM nO3 with x less than or equal to 0.17 has been studied in detail using neutron diffraction. It has been established that this system has two orthorhombic phases. One is the O' phase with bl root 2<c<a and with- static Jahn-Teller (JT) distortions, while the other is a pseudocubic phase with bl root 2 similar to a similar to c, which we call the O p hase. In-particular, the x=0.125 sample exhibits O-->O'-->O* reentran t structural transitions. For 0.10 less than or equal to x less than o r equal to 0.17 a ferromagnetic ordering strongly suppresses lattice d istortions at and below the ferromagnetic transition temperature. Thes e results demonstrate a strong coupling between structural distortion, ferromagnetic ordering, and transport properties in the insulating La 1-xSrxMnO3 system.