Triple A-Site Cation Ordering in the Ferrimagnetic Y(2)CuGaMn(4)O(12) Perovskite

[Image: see text] A new member of A-site columnar-ordered A(2)A′A″B(4)O(12) quadruple perovskites with the composition of Y(2)CuGaMn(4)O(12) was prepared by a high-pressure, high-temperature method at 6 GPa and about 1500 K. Its crystal structure and cation distributions were studied by powder synchrotron X-ray and neutron diffraction. There is a triple A-site cation ordering with some degrees of anti-site disorder among sites occupied by 3d transition metals: [Y(2)](A)[Cu(0.8)Mn(0.2)](A′)[Ga(0.8)Mn(0.2)](A″)[Mn(3.6)Cu(0.2)Ga(0.2)](B)O(12). It has the space group P4(2)/nmc (no. 137) between 1.5 and 873 K with a = 7.33884 Å and c = 7.66251 Å at 297 K. Despite anti-site disorder, it exhibits a long-range ferrimagnetic order at T(C) = 115 K with the ordered moment of 2.19 μ(B) at each B site and 0.89 μ(B) at the A′ or A″ site. Magnetic moments are aligned along the c axis; all moments are ordered ferromagnetically at the B sites, and the moments at the A′ or A″ site are ordered in the opposite direction. Cu(2+) doping drastically changes magnetic properties as “parent” Y(2)MnGaMn(4)O(12) just shows spin-glass magnetic properties without long-range ordering. Anisotropic thermal expansion was observed in Y(2)CuGaMn(4)O(12): the lattice parameter a almost linearly decreases from 1.5 K to T(C) and then monotonically increases up to 873 K (almost linearly from 300 K); the parameter c monotonically increases from 1.5 to 300 K and then decreases up to 600 K.