Ambient pressure synthesis and magnetic properties of La[Cu3−xMnx][Mn4−yTiy]O12 (x = 0 & 1; y = 0.5 & 1) quadruple perovskite

Highlights: • Ambient pressure synthesis of very low Ti-content quadruple perovskites. • Morphology of LaCu₃Mn_3.5Ti_0.5O₁₂ particles reveals unusual step-terrace type growth. • XPS study revealed the mixed cation occupancy in both A- and B-sites. • Mixed occupancy of Cu²⁺ and Mn³⁺ ions in A-site strongly affect ferrimagnetic T_C. • Competing magnetic interactions leads to re-entrant spin glass behavior at lower temperature. -- Abstract: Ambient pressure synthesis of very low Ti-content quadruple perovskites LaCu₃Mn_3.5Ti_0.5O₁₂, 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 LaCu₃Mn_3.5Ti_0.5O₁₂ particles reveals unusual step-terrace type growth. XPS studies revealed the mixed occupancy of Cu²⁺ and Mn³⁺ ions in A-site. The ferrimagnetic T_C 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 T_C 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.