The crystallographic and magnetoresistance of CaF2 doped Nd0.67Sr0.33MnO3 compounds

We have studied crystal structures and the giant magnetoresistance of fluor ide Nd0.67Sr0.33MnO3 compounds, The experimental results show that the CaF2 dopant can stabilize the original crystal structure of Nd0.67Sr0.33MnO3 co mpounds. The lattice spacings and unit cell volumes of these fluoride compo unds decrease with CaF2 doping. The Rietveld profile fitting technique has been used to refine the crystal structures of these compounds. The space gr oup of those compounds is Pbnm, Z=4, The F anion prefers to occupy the 8d c rystal position, All of these fluoride compounds are ferromagnetic; their C urie temperatures decrease with CaF2 doping. However, the giant magnetoresi stance ratio of these fluoride compounds increases; A magnetoresistance rat io as high as 99.2% is obtained at an applied field of 5T. (C) 1999 Academi c Press.