On the Magnetotransport Properties and Griffith Phase in the (La, Gd)1.4(Ca, Sr)1.6Mn207 Double-Layered Manganites

The double-layered manganite La1.2Gd0.2Ca1.2Sr0.4Mn2O7 was prepared by the solid-state reaction route, and its structural, microstructural, magnetic, electrical, and magnetotransport properties were investigated. Rietveld refinement analysis of the X-ray diffractogram shows that the structure is indexed in a tetragonal structure with an I4/mmm space group with an impurity phase. The microstructure was examined using scanning electron microscopy. The purity of the sample was examined by the energy-dispersive X-ray spectroscopy investigation. In the context of magnetic measurements, inverse susceptibility, hysteresis loop, and the magnetic behavior of the compound are discussed in detail. The sample displays a phase transition from ferromagnetic (FM) to paramagnetic (PM) at T-C, which is equal to 290.13 K. Additionally a Griffith phase (GP) was identified and was found to be 339 K. The sample can be thought of as spin-glass-like since a significant divergence was observed at low temperatures between the magnetization curves M (T) in the zero-field cooling (ZFC) and in the field cooling (FC) modes. The electrical resistivity under an applied magnetic field of 1 T exhibits a metal-insulator transition (T-MI) at 152.98 K. The magnetoresistance was observed to decrease with increasing temperature, peaking at 23% at 11 K. The electrical resistivity in the ferromagnetic region ( T < T-MI) has been found to be a combination of residual resistivity and resistivities due to the weak localization, and to the electron-electron, while the adiabatic small polaron and variable range hopping models may be used to explain the resistivity data at high temperature in paramagnetic region ( T > T-MI).