Order-disorder phase transition in Zn1ÀxMnxGa2Se4 : Long-range order parameter versus x
نویسندگان
چکیده
The opportunity of the Zn12xMnxGa2Se4 (0<x<1) series for exploring the possibilities of orderingdisordering processes as a function of x is shown. A pumping of Mn ions from one particular site of the crystal lattice to another occurs in this system on addition of Zn. As a consequence, the tetragonal diluted magnetic semiconductor Zn12xMnxGa2Se4 series exhibits an order-disorder phase transition at xc50.506 .01 with (c/a)c51.9646 .005. The disordering process is accompanied by an abrupt change in the tetragonal unit cell parameters c and 2-(c/a), a modification of the crystal lattice from defective chalcopyrite to defective stannite and a crossover from space group I-4 to I-42 m. The order-disorder phase transition has been quantified through the direct determination of a long-range order parameter h within its whole range of existence (0<h<1).
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