Abstract
The transport properties of the manganites with and of Fe-doped samples have been comprehensively studied using magnetoresistance measurements, and Mössbauer spectroscopy, and x-ray diffraction. At the Sn concentration is a single phase. The manganites with consist of two phases, and ; the chemical formulas are and , respectively. The colossal magnetoresistance (CMR) in appears to have its origin in deficient La and/or Mn ions in the phase. Mössbauer spectra show that a superparamagnetic doublet exists from for the phase in the Fe-doped sample and may have superparamagneticlike spin clusters that lead to a low saturation field. Consequently, the CMR reaches 75% at an applied field of only 20 kOe for the Fe-doped sample; however, the same CMR requires fields as high as 70 kOe in the undoped sample.
- Received 22 April 1999
DOI:https://doi.org/10.1103/PhysRevB.60.10284
©1999 American Physical Society