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Effects of cation disorder and strain on the surface morphologies and transport properties of thin films with different A-site cation disorder, which was achieved by Y and Sr codoping into La2/3Ca1/3MnO3, have been investigated. A metal-insulator transition (MIT) was observed on all films except that on MgO, which indicates that large strain increases insulator phase. With increasing cation disorder, the resistivity increases while MIT and Curie temperature decrease, which reveal that cation disorder suppresses the long-range ferromagnetic metallic phase. The spin-glass state and ferromagnetic-metallic state coexist in low temperature. Cation disorder induces more insulator phases in the large strain films. A Kondo-like transport behavior was observed in the large cation disordered films. [ABSTRACT FROM AUTHOR]

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]