Weak ferromagnetism and domain wall motion in a linear magnetic polymer

Susceptibility measurements from dc to 500 kHz have been made on the linear coordination polymer, poly(cobalt n-butylphosphinate). At high temperature the data conform to the classical Heisenberg antiferromagnetic chain with a mean field temperature of 28 K. Below about 20 K there is an excess susceptibility which saturates in modest fields. These results are described in terms of an antisymmetric exchange component which produces short-range weak ferromagnetic order in the paramagnetic phase. At still lower temperature the ac susceptibility shows a loss component, even in zero applied field, which we ascribe to the motion of domain walls in the weak ferromagnetization.