PHASE SEPARATION INDUCED BY CATION DISORDER IN (La, Y)2/3(Sr, Ca)1/3MnO3.

Polycrystalline manganite oxides with different A-site cation disorder were synthesized. The hole concentration and average radius of A-site cation are kept unchanged while the A-site cation disorder increases linearly by Y and Sr co-doped in La2/3Ca1/3 MnO3. All these samples exhibit a paramagnetic insulator to ferromagnetic (FM) metal transition, and the transition temperature TC and TMI decrease while the transition width increases with increasing the A-site cation disorder. TMI is usually 10 K higher than TC for the small cation disorder samples. However, with increasing the cation disorder, TMI is about 60 K lower than TC, and the resistivity increases in magnitude while the magnetization decreases. The metal-to-insulator transition for samples with small cation disorder can be well described by a percolative model, which indicates FM-metal state and antiferromagnetic insulator state assuredly coexist in the transition interval. It reveals that cation disorder suppresses the long-range FM-metal state which results in the phase separation behavior in samples with large cation disorder. [ABSTRACT FROM AUTHOR]