Resurgence of ferromagnetic behavior coupled with Griffiths singularity in the electron doped La0.3Ca0.7MnO3 compound following the creation of oxygen deficiency

Abstract

We report the effect of the oxygen deficiency on the structural and magnetic properties of La0.3Ca0.7MnO3-δ (0 ≤ δ ≤ 0.2) perovskites. The parent compound (δ = 0) was prepared by the solid- state reaction. This sample was used to prepare the oxygen deficiency compounds using iron as oxygen absorber. The X-ray diffraction (XRD) data have been analyzed by the Rietveld method using the FullProf program. We have noticed that all samples crystallized in the orthorhombic structure with Pbnm space group. Magnetic measurements show that the parent compound La0.3Ca0.7MnO3 exhibits a paramagnetic behavior at high temperature and an antiferromagnetic state (AFM) coupled with charge ordering (CO) at low temperature. With oxygen deficiency a magnetic transition from paramagnetic (PM) to ferromagnetic (FM) state is fixed at decreasing temperature. The compound with δ = 0.15 exhibit a PM-FM transition when decreasing the temperature at TC = 191 K with persistence of the charge ordering state at low temperatures below 81 K. The compound with δ = 0.2 exhibit a PM-FM transition when the temperature decreases at TC = 134 K with vanishing of the CO state at low temperature. Further investigations of the magnetization measurements reveal features consistent with the appearance of Griffiths phase (GP) in the sample with δ = 0.15 and δ = 0.2 which proves the existence of ferromagnetic clusters in the paramagnetic domain below TG = 250 K and 234 K for δ = 0.15 and δ = 0.2 respectively.