Photoluminescence and magnetism in the new magnetic semiconductors: K2Cd3((1-x))Mn3xS4

A new family of magnetic semiconductors, K2Cd3((1-x))Mn3xS4, prepared from molten K2Sx is reported. For x less than or equal to 0.6, the compounds cry stallize in the K2Cd3S4 structure type. The cell volumes of the series obey Vegard's Law for solid solutions. The compounds range in color from yellow through orange brown to red and possess platelike morphologies. A structur al transformation occurs between x = 0.7 and x = 0.9. Red plates of K2Cd0.4 Mn2.6S4 (x = 0.87) crystallize in the space group Ccca with a = 5.9217(8) A ngstrom, b = 13.531(1) Angstrom, c = 11.0696(8) Angstrom, and V = 887.0(1) Angstrom (3). The end member, K2Mn3S4, crystallizes in the space group Ccca with a = 11.0637(7) Angstrom, b = 26.830(2) Angstrom c = 5.8180(4) Angstro m, and V = 1727 Angstrom (3). For x less than or equal to 0.6, the compound s form as (M3S4)(n)(2n-) layers, interspersed by K+ cations. These layers a re composed only Of M3S42- units shaped like truncated cubes. When x = 0.87 , a new structure related to that Of Cs2Mn3S4 is observed. The end member o f the series (i.e., x = 1) K2Mn3S4 is revealed to have a related yet surpri sing structure. The compounds display room-temperature band gaps ranging fr om 2.79 to 2.92 eV. Absorptions in the mid-gap region, due to Mn2+-based d- d transitions, are also observed. The compounds are strongly emissive in th e visible spectrum at room temperature, with the light emission shifted to the red immediately upon the introduction of small amounts of manganese. Th e magnetic properties of these compounds evolve from classical paramagnetic to spin glass as a function of x. For x greater than or equal to 0.05, the compounds deviate from Curie-Weiss behavior. Antiferromagnetic coupling is observed in all cases. With very high Mn content transitions to magnetical ly complex phases are observed with possible spin-glass-like behavior.