Photoluminescence and Magnetism in the New Magnetic Semiconductors: K 2 Cd 3(1 - x ) Mn 3 x S 4
2001; American Chemical Society; Volume: 13; Issue: 9 Linguagem: Inglês
10.1021/cm0100422
ISSN1520-5002
AutoresEnos A. Axtell, Jason A. Hanko, J. A. Cowen, Mercouri G. Kanatzidis,
Tópico(s)Advanced Condensed Matter Physics
ResumoA new family of magnetic semiconductors, K2Cd3(1-x)Mn3xS4, prepared from molten K2Sx is reported. For x ≤ 0.6, the compounds crystallize 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 structural transformation occurs between x = 0.7 and x = 0.9. Red plates of K2Cd0.4Mn2.6S4 (x = 0.87) crystallize in the space group Ccca with a = 5.9217(8) Å, b = 13.531(1) Å, c = 11.0696(8) Å, and V = 887.0(1) Å3. The end member, K2Mn3S4, crystallizes in the space group Ccca with a = 11.0637(7) Å, b = 26.830(2) Å c = 5.8180(4) Å, and V = 1727 Å3. For x ≤ 0.6, the compounds form as (M3S4)n2n- layers, interspersed by K+ cations. These layers are 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 of the series (i.e., x = 1) K2Mn3S4 is revealed to have a related yet surprising structure. The compounds display room-temperature band gaps ranging from 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 the visible spectrum at room temperature, with the light emission shifted to the red immediately upon the introduction of small amounts of manganese. The magnetic properties of these compounds evolve from classical paramagnetic to spin glass as a function of x. For x ≥ 0.05, the compounds deviate from Curie−Weiss behavior. Antiferromagnetic coupling is observed in all cases. With very high Mn content transitions to magnetically complex phases are observed with possible spin-glass-like behavior.
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