An effort to develop La manganites for possible sensor applications has led to the successful growth of La, 1-xB xMnO 3-δ (B=Sr, Ca) thin films on single crystal MgO, Al 2O 3, and LaAlO 3 substrates. Here we concentrate on Sr-doped material on LaAlO 3 with Curie temperature T c=262±2 K. T c was determined from magnetization measurements using Arrott plots, and agrees well with the observed resistivity peak in zero applied magnetic field (H). This T c corresponds closely to a Sr content x=0.17 reported in bulk materials. At H=60 kOe the maximum magnetoresistance Δρ/ ρ≈0.95. No discernible hysteresis, as might be expected for structural phase transitions, was observed. When plotted as a function of reduced temperature T/T c, the magnetization extrapolated , to zero H is best fit by a Brillouin function with an effective spin value 〈S〉 much larger than the 〈S〉= 1.9 indicated by the composition. This may be indicative of magnetic polaron formation, especially near the magnetic and transport transition temperatures. At temperatures far below T c there is an increase in resistivity of the thin films, which is considerably modified by the application of a field of 50 kOe. The conductivity, however, remains finite as the temperature approaches zero, indicating transport in states close to but above the mobility edge.
|Number of pages||3|
|Journal||Journal of Applied Physics|
|Issue number||8 PART 2B|
|Publication status||Published - 15 Apr 1997|
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)
- Physics and Astronomy(all)