Structural, magnetic, and transport properties in a Cu-doped La[sub 0.7]Ca[sub 0.3]MnO[sub 3] system.

The structural, magnetic, and transport properties of La[sub 0.7]Ca[sub 0.3]Mn[sub 1 - x]Cu[sub x]O[sub 3] (0 ≤ x ≤ 0.2) have been investigated. The maximum magnetoresistance (MR) is about 4 × 10[sup 6]% for the sample with x = 0.15, which is about ∼10[sup 4] times the maximum MR for samples with x ≤ 0.1. A change in the structural parameters and magnetic and resistivity properties of the samples shows that Cu exists in Cu[sup 3+] ionic form in the sample with x ≤ 0.05. However, Cu[sup 2+] ions begin to appear and then they increase with further Cu doping. [ABSTRACT FROM AUTHOR]