OBSERVATION OF THE FLUX-LINE-LATTICE IN (LA1-XSRX)(2)CUO4 SINGLE-CRYSTALS

Small angle neutron diffraction was used to image the flux line lattic e (FLL) in a large superconducting (La1-xSrx)(2)CuO4 (La-2 1 4) single crystal for the first time. Diffraction patterns were obtained in fie lds up to 0.2 T and at several temperatures (3-26 K). We find an inten sity ring instead of peaks, which proves the existence of a polycrysta lline flux line lattice in La-2 1 4. We relate this observation to the structural phase transition of the compound at about 200 K, which des troys the single crystalline character of the sample in the plane perp endicular to the c-axis. (C) 1998 Elsevier Science Ltd. All rights res erved.