Ai. Tovstolytkin et al., Unusual substitutional properties of Cu in bulk polycrystalline samples ofLa0.7Ca0.3Mn1-xCuxO3-delta, LOW TEMP PH, 27(5), 2001, pp. 366-371
The transport and magnetoresistive properties of bulk polycrystalline sampl
es of the La0.7Ca0.3Mn1-xCuxO3-delta (x less than or equal to0.15) system a
re studied in the temperature range 77 K-300 K. All the samples investigate
d exhibit the giant magnetoresistance effect associated with the transition
from the ferromagnetic metallic to the paramagnetic insulating state. As a
function of copper concentration, the temperature T-p of the resistivity p
eak first decreases from 193 K (x=0) to 108 K (x=0.10) and then gradually g
rows, reaching 120 K at x=0.15. Significant temperature broadening of the r
esistive transition as well as anomalous behavior of the peak value of the
resistivity are observed near x=0.10. The unusual properties of the La0.7Ca
0.3Mn1-xCuxO3-delta system are well explained in terms of a mixed valence o
f the Cu ions. (C) 2001 American Institute of Physics.