Structural and Magnetic Properties of A-Site-Ordered Perovskites ACu3Sn4O12 with A = Ca2+, Sr2+, and Pb2+
文摘
A series of A-site-ordered perovskites ACu3Sn4O12 with A = Ca2+, Sr2+, and Pb2+ were prepared under high-temperature and high-pressure conditions. They have Cu2+ ions with S = 1/2 spins at the A site in the ABO3 perovskite structure and have nonmagnetic Sn4+ ions at the B sites. An increase in the size of the divalent A-site ions from Ca to Pb increases the cubic lattice constant by only 0.6%. The cubic lattice with rigid CuO4 units thus hardly expands and the different sizes of the A-site ions are accommodated by change of the SnO6 octahedra. The difference in the size of the A-site ions has little effect on the ferromagnetic transition temperatures, because the magnetic properties of these perovskites are determined primarily by the direct ferromagnetic interaction between Cu2+ ions at the A site.