Magnetic phase transitions leading to Griffith’s singularity with electrical and dielectric anomalies in transport properties of LaMnO3+δ

The polycrystalline LaMnO3+δ has been investigated and studied in detail for its structural, magnetic, electrical transport and dielectric properties. Perovskite manganites like LaMnO3+δ is intrinsically inhomogeneous and exhibit disorders, which lead to different types of critical phenomenon. The magnetization measurement suggests the occurrence of Griffith’s phase (means no clear phase separation in this region) like phenomenon arising above critical temperature TC. This is also reflected as a small hump in electrical resistivity measurement about the same temperature as observed in magnetization measurements. The occurrence of Griffith’s phase-like phenomenon arising above the critical temperature TC in LaMnO3+δ manganites is found due to the quenched disorder in the co-operative interactions of the frustrated magnetic spins. The analysis of electrical resistivity measurements further suggests that the transport properties in this region follows Shklovskii–Efros variable range hopping (SE-VRH) mechanism, as the sample encompass disorder and frustration. The Magneto-resistance (MR) at different temperatures measured with respect to the applied magnetic field further concludes the characteristic dependent on Brillouin function. The Dielectric measurements carried out on the sample exhibits multiple relaxation behavior, which is understood using combined Debye-Maxwell Wagner relaxor dynamics.