Dielectric and Spin-Glass Magnetic Properties of the A-Site Columnar-Ordered Quadruple Perovskite Sm2CuMn(MnTi3)O12

Perovskite-type ABO(3) oxides show a number of cation-ordered structures, which have significant effects on their properties. The rock-salt-type order is dominant for B cations, and the layered order for A cations. In this work, we prepared a new perovskite-type oxide, Sm2CuMn(MnTi3)O-12, with a rare columnar A-site order using a high-pressure, high-temperature method at about 6 GPa and about 1700 K. Its crystal structure was studied with synchrotron powder X-ray diffraction. The compound crystallizes in space group P4(2)/nmc (No. 137) at room temperature with a = 7.53477 angstrom and c = 7.69788 angstrom. The magnetic properties of the compound were studied with dc and ac magnetic susceptibility measurements and specific heat. Spin-glass (SG) magnetic properties were found with T-SG = 7 K, while specific heat, in the form of C-p/T, showed a strong, very broad anomaly developing below 20 K and peaking at 4 K. The dielectric constant of Sm2CuMn(MnTi3)O-12 was nearly frequency and temperature independent between 8 K and 200 K, with a value of about 50. Cu2+ doping drastically modified the magnetic and dielectric properties of Sm2CuMn(MnTi3)O-12 in comparison with the parent compound Sm2MnMn(MnTi3)O-12, which showed a long-range ferrimagnetic order at 34-40 K. The antisite disorder of Cu2+ and Mn2+ cations between square-planar and octahedral sites was responsible for the SG magnetic properties of Sm2CuMn(MnTi3)O-12.