Observation of a 1/3 magnetization plateau in Pb 2 Cu 10 O 4 (SeO 3 ) 4 Cl 7 arising from (Cu 2+ ) 7 clusters of corner-sharing (Cu 2+ ) 4 tetrahedra.

A mixed-valence compound Pb 2 Cu 10 O 4 (SeO 3 ) 4 Cl 7 has a complex structure consisting of one nonmagnetic Cu + ( S = 0) ion and four nonequivalent magnetic Cu 2+ ( S = 1/2) ions. It exhibits antiferromagnetic ordering at T N = 10.2 K. At a temperature below T N , a sequence of spin-flop transition at B spin-flop = 1.3 T and 1/3 plateau formation at B spin-flip = 4.4 K is observed in the magnetization curve M ( B ). The 1/3 magnetization plateau persists at least up to 53.5 T. The spin exchanges of Pb 2 Cu 10 O 4 (SeO 3 ) 4 Cl 7 evaluated by performing energy-mapping analysis based on DFT+U calculations show that the magnetic properties of Pb 2 Cu 10 O 4 (SeO 3 ) 4 Cl 7 are described by the (Cu 2+ ) 7 cluster of corner-sharing (Cu 2+ ) 4 tetrahedra, and that each (Cu 2+ ) 7 cluster has a S = 3/2 spin arrangement in the ground state. The 1/3 magnetization plateau observed for Pb 2 Cu 10 O 4 (SeO 3 ) 4 Cl 7 is explained by the field-induced flip of every second (Cu 2+ ) 7 cluster within a unit cell.