Low-field magnetoresistance and switching behavior of polycrystalline La0.66Sr0.34MnO3/YSZ(001) films with columnar grain structure

Abstract

The La0.66Sr0.34MnO3 (LSMO) films with thickness d = 180–330 nm were grown by radio frequency magnetron sputtering on cubic yttria-stabilized zirconia, YSZ(001), at 750 °C. Coexistence of columnar grains with the averaged diameter of about 50 nm and (001) and (011) planes of a pseudocubic lattice oriented parallel to the film surface has been certified by transmission electron microscopy and x-ray diffraction investigations. Pole figure x-ray diffraction measurements revealed cube-on-cube growth of the LSMO(001) grains on YSZ(001) with 45° in-plane rotation meanwhile two in-plane orientations with the epitaxial relationships: [001]LSMO//[010]YSZ and [001]LSMO//[100]YSZ have been certified for the LSMO(011) grains. Presence of high-angle grain boundaries between the columnar grains resulted enhanced electrical resistivity and low-field magnetoresistance associated to spin-polarized tunnelling of carriers. Electrical resistance versus magnetic field plots demonstrated the characteristic hysteresis behavior in the low field region (H b 80 kA/m) with peak-like maxima at H = ±Hp. An unusual sharp resistance drop at H ≅ Hp indicated for the films at T b 210 K and the observed variation of Hp with the angle between applied field and the film plane (α) defined by the Kondorsky relationship: Hp = Hp0/cosα demonstrate strong pinning of domain walls at grain boundaries.