Order-disorder phase transition in Zn1-xMnxGa2Se4:: Long-range order parameter versus x -: art. no. 125208

The opportunity of the Zn1-xMnxGa2Se4 (0less than or equal toxless than or equal to1) series for exploring the possibilities of ordering-disordering 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 Zn1-xMnxGa2Se4 series exhibits an order-disorder phase transition at x(c)=0.50+/-.01 with (c/a)(c)=1.964+/-.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 eta within its whole range of existence (0less than or equal toetaless than or equal to1).