MAGNETIC AND STRUCTURAL-PROPERTIES OF KCOXMG1-XF3 COMPOUNDS

The mixed crystals KCoxMg1-xF3 with 0.25 < x < 1 were studied by stati c susceptibility and X-ray diffraction methods, in the temperature ran ge 4.2-350 K. From these measurements, the variations of several quant ities, viz. T-N, t = T-N(X)/T-N(1), theta (Curie-Weiss temperature), m u(eff) (effective moment), and a, c (lattice parameters) with concentr ation or temperature were determined. The exchange constant was evalua ted using theoretical results obtained for random, dilute magnetic sys tems with magnetic ions having nonvanishing orbital momenta. From the temperature evolution of the cubic (400) Bragg line, the values of tem perature for the structural phase transition and tetragonal deformatio n lattice with c/a < 1 were estimated. A strong correlation was found between the magnetic and structural phase transition, with the lattice deformation resulting from the magnetic properties of the crystals st udied.