THE SUBSTITUTION OF VANADIUM BY CHROMIUM IN THALLIUM PENTAVANADIUM OCTASULFIDE .3. MAGNETIC-PROPERTIES

The investigation of the magnetic properties of the substitution serie s TlV5-yCryS8 (1 less than or equal to y less than or equal to 4) reve aled a complex magnetic behaviour due to the successive formation of C r-2-dimers. The Cr atoms within the dimers are antiferromagnetically c oupled and with raising Cr content the coupling constant becomes more negative indicating stronger antiferromagnetic exchange interactions. The magnetic behaviour is further characterized by a Curie-Weiss like contribution from nearly isolated Cr atoms and a temperature independe nt paramagnetism (TIP) from delocalized conduction electrons. With inc reasing substitution of V by Cr the TIP decreases and the magnetic mom ent per Cr atom increases. In addition, the evaluation of the magnetic susceptibilities gives hints for a preferential occupation of the thr ee different crystallographic sites by the Cr atoms.