EXCHANGE INTERACTIONS IN POLYMETALLIC ORGANOSILOXANES

Iron (3 +) and cobalt (2 +) polyorganosiloxanes were synthesized and c haracterized magnetically. The cobalt-containing polymers have a ferro magnetic ground state with a mean value of J below 10 K. On the other hand, iron-containing polymers demonstrate both ferromagnetic coupling with mean J values ranging from 5 to 70 K (depending on the Fe concen tration) and antiferromagnetic interaction with an exchange constant h aving an absolute magnitude of about 10 times less, Several models wer e developed to fit the experimental data. For both systems the best mo del found was the following: ion-ion coupling for Fe (spin 5/2) and fo r Co (spin 3/2) arising from interactions within the polymeric chain, complicated by inter-chain interactions which are positive and negativ e for Co and Fe, respectively. A molecular field approximation was use d to calculate the contribution of this interaction.