Local structural distortion and magnetotransport properties of Nd_0.5Pb_0.5-xSr_x (Mn, Fe)O₃

Structural and magnetotransport properties of Fe-doped Nd_0.5Pb_0.5-xSr_x (Mn, Fe)O₃ are investigated by means of x-ray diffraction (XRD), M?ssbauer spectroscopy and transport measurements. Both XRD patterns and M?ssbauer spectra indicate that structural distortion decreases with Sr doping. Furthermore, it is found that Sr doping results in decrease of the resistivity at room temperature and increase of magnetoresistance. In samples, the same ratio of Mn³⁺ to Mn⁴⁺ is kept. So we would rather attribute these changes to the local structural distortion than the double exchange (DE) interaction. The local structural distortion of the Mn(Fe)O₆ octahedron which results from the Jahn—Teller effect, can localize the conduction electrons. In this regard, we provide another evidence to prove that this Jahn—Teller distortion is an important factor that affects the transport property above T_c besides the DE coupling.