Mixed magnetic exchange interactions and ferromagnetic diffuse phase transition of La1−xMnO3+δ manganites

Effects of vacancy on the microstructural and magnetic properties in self-doped La1−xMnO3+δ (x ≤ 0.3) manganites have been studied. The samples crystallize in a single phase of rhombohedral structure exhibiting R3C space group until x-value reaches 0.2. As self-doped concentration increases, structural distortion is confirmed by combining X-ray diffraction. Ferromagnetic (FM) and antiferromagnetic (AFM) coupling is found and exchange bias effect appears at low temperature. Ferromagnetic diffuse phase transition (FDPT) is induced by Griffiths phase for x ≥ 0.1 at temperature of T > TC. The FM transition temperature range is increased from 32 K to 150 K. The enhancement of Griffiths phase with x for x ≥ 0.1 is explained by the greater A-site spatial disorder and the structural distortion.