Structural, magnetic, and transport properties of Zr-substituted La0.7Sr0.3MnO3

Zr-substituted perovskites La0.7Sr0.3Mn1-xZrxO3 with 0 <= x <= 0.20 were investigated by neutron diffraction (ND), magnetization, electric resistivity, and magnetoresistance measurements. ND refinements reveal that substituted Zr4+ goes only to the Mn site. Because of its large size, this leads to a Zr-solubility limit at x <= 0.10. The x <= 0.10 samples exhibit a rhombohedral structure (space group R(3)over-bar-c) from 10 K to room temperature. For the x <= 0.10 samples, the cell parameters a and c, and volume increase continuously with increasing Zr content. In addition, the structural distortion of the MnO6 octahedra increases with increasing Zr content. Zr-substituted La0.7Sr0.3MnO3 exhibits metallic behavior at low temperature. The field dependent resistivity suggests that electron-electron scattering is dominant and a two-magnon scattering process emerges with increasing temperature. The contribution from the two-magnon scattering in resistivity becomes larger with increasing Zr content. A maximum magnetoresistance (MRmax) of 35% is obtained for the x=0.03 sample at H=5 T. The MRmax shifts to a higher temperature region upon application of an external magnetic field. (c) 2007 American Institute of Physics.