Fluorination of La2−xSrxCuO4 (x = 0, 0.15, 0.3) and study on the crystal structures, magnetic properties of their fluorinated products

Abstract Here we report using the transition metal difluoride ZnF 2 to fluorinate K 2 NiF 4 -type cuprates La 2− x Sr x CuO 4 ( x  = 0, 1.5, 0.3). Unlike other fluorinating agents, the technique is nontoxic, easy to handle and the byproduct ZnO can be removed. After fluorination, the fluorinated product of La 2 CuO 4 suffers a phase transformation and unit cell expansion. While La 1.85 Sr 0.15 CuO 4 and La 1.7 Sr 0.3 CuO 4 indicate no change in structure after fluorination, their space groups still are I/4mmm, however, their lattices become larger, too. We emphasis the structural characterizations for fluorinated product of La 1.7 Sr 0.3 CuO 4 by high-resolution transmission electron microscopy (HRTEM) images and electron diffraction (ED) patterns. Moreover, we determine the chemical formula to be La 1.54 Sr 0.46 CuO 3.1 F 0.9 and the fluorine ions are prone to be located in the apical sites of the Cu(O, F) 6 octahedron in the structure of post-treated fluorinated product of La 1.7 Sr 0.3 CuO 4 . Magnetization investigations demonstrate that partial replacement of the lanthanum by strontium changes the magnetism of post-treated fluorinated products of La 2− x Sr x CuO 4 ( x  = 0, 0.15, 0.3) and they exhibit a paramagnetic behavior.