Abstract
Ambient pressure synthesis of very low Ti-content quadruple perovskites LaCu3Mn3.5Ti0.5O12, LaCu2Mn4TiO12 and LaCu3Mn3TiO12, has been carried for the first-time using sol-gel process. All the samples were characterized using X-ray diffraction, Field Emission Scanning Electron Microscope imaging (FE-SEM), Energy Dispersive X-ray Analysis (EDX), X-ray photoelectron spectroscopic (XPS) studies and temperature dependent magnetic measurement of both the a.c and d.c magnetization. All the compositions crystallized in a cubic I-m3 space group. EDX analysis confirms the nominal cationic composition and chemical homogeneity of the samples. Morphology of LaCu3Mn3.5Ti0.5O12 particles reveals unusual step-terrace type growth. XPS studies revealed the mixed occupancy of Cu2+ and Mn3+ ions in A-site. The ferrimagnetic TC as well as saturation magnetization rapidly increases with the decrease in Ti-content. The onset of ferrimagnetism is ascribed to the antiferromagnetic coupling between the moments in A-site and moments in B-site. The downward deviation of TC from linearity with respect to Ti-free composition can be ascribed to the mixed occupancy of Cu2+ and Mn3+ ions in A-site. Low temperature re-entrant spin glass state is associated with the spin frustration in B-site due to competing interaction between mixed valencies, interruption in exchange path by non-magnetic Ti4+ cation and structural aspect.
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