Spin-glass to long-range order to spin-glass evolution of magnetic properties with the composition in Sm2MnZnMn4−xTixO12 (x = 1, 2, and 3) perovskites

Sm2MnZnMn4−xTixO12 perovskites with x = 1, 2, and 3 were synthesized by a high-pressure, high-temperature method at 6 GPa and about 1700 K. They belong to a subfamily of perovskite materials with a general composition of A2A′A′′B4O12, where the A′ site has a square-planar coordination and the A′′ site has a tetrahedral coordination. The x = 1 and 3 samples were investigated by powder synchrotron X-ray diffraction, and it was found that triple A-site cation ordering was realized in the x = 1 sample (having only Mn3+ cations) with Zn2+ cations located in the A′′ site and with a very small degree of antisite disorder between the A and A′ sites. An additional antisite disorder takes place in the x = 3 sample (having only Mn2+ cations) between the A′′ and B sites. The three compounds crystallize in space group P42/nmc (No. 137) at room temperature with a = 7.39810 Å and c = 7.92180 Å (x = 1), a = 7.50656 Å and c = 7.79545 Å (x = 2), and a = 7.61311 Å and c = 7.68145 Å (x = 3). Unusual evolution of magnetic properties was found as spin-glass-like properties were observed at TSG = 21 K in the x = 1 sample with the largest Mn content and at TSG = 6.5 K in the x = 3 sample with the smallest Mn content. On the other hand, a long-range ferrimagnetic order takes place in the x = 2 sample at TC = 18 K with an intermediate Mn content. Zn doping significantly modifies magnetic properties of Sm2MnZnMn4−xTixO12 in comparison with the ‘parent’ compounds Sm2MnMnMn4−xTixO12.