Structural,electrical, magnetic and NMR study of the NaxCrxTi1−xS2 system

Two phases are characterized in the Na_xCr_xTi_1?xS₂. The first one spans the composition range 0.34 < x < 0.71, the alkali-metal ions occupying trigonal prismatic sites. The second one which is isotypic with NaCrS₂ is found in the range 0.87 < x ? 1, the alkali-metal ions being this time in octahedral sites. Electrical measurements performed by the complex impedance method show that the conductivity is thermally activated. Magnetic and NMR experiments indicate the existence of localized magnetic moments on the chromium ions. These moments induce a shift of the NMR line and produce the most important contribution to the relaxation. The variation of the Curie temperature seems to indicate a continuous weakening of the ferromagnetic coupling between chromium ions of the same layer as the number of chromium ions decreases. An antiferromagnetic coupling then becomes preponderant.